PLK computer SIR: (XI) Ch-1 Computer System

1.1.1 Def, Characteristics and application of Computer	1.1.2 Evolution of Computer
1.1.3 Measure of speed and storage unit of Computer	1.1.4 Classification of Computer
1.1.5 Mobile Computing	1.2.1 Concept of Computer architecture and organization
1.2.2 Components of Computer System	1.2.3 Microprocessor
1.2.4 Bus System	1.2.5 Primary Memory
1.2.6 Secondary Memory	1.2.7 Input Devices
1.2.8 Output Devices	1.2.9 Hardware Interfaces

1.1.1 Definition , characteristics and applications of computer

The word “Computer” is derived from the Latin word “Computare” which means to calculate.
Definition of Computer: - An electronic device which accepts raw data from users and processes it to give meaningful results and store the important data for future use is called Computer.
Data: - The raw facts about anything are called data. Examples: Students data are name, address, class, roll no. etc.
Instruction: - Instruction is specifying what must be done to the data.
For examples: SP = 1000 and CP = 700 are data. To find profit (SP>CP) = SP-CP =1000-700= 300
Information: - The processed data which gives meaningful results is called information. Example: 300 is profit.
Hardware:- Computer hardware is the collection of physical components that make up a computer. In other words we can say that hardware covers all parts of a computer that are tangible objects. Examples of hardware are input devices like keyboard and mouse, output devices like printer and monitor, storage devices like disk drive and the computer itself.
Software:- Software refers to the component of the computer which do not have a material form, such as programs, data, protocols etc. Software refers to something intangible. Basically, software is a program written by a programmer which controls/operates specific parts of the computer or specific application. Software is often divided into two categories:
System software:- It includes operating system and all utilities that enable the computer to function.
Application software:- It includes programs that do real work for users. For example, word processors, spreadsheets, and database management systems fall under the category of application software.
Firmware:- A set of micro instructions stored in a chip is called firmware. Micro instructions are hardware level instructions which are directly executed by the hardware. Firmware is loaded into the equipment, either at the time it is manufactured or later, by the person installing the equipment or the person using it. In other words, Firmware, which is added at the time of manufacturing, is used to run user programs on the device, Firmware is a combination of software and hardware. ROMS, PROMS and EPROMS that have data or programs recorded on them are firmware. The best example of firmware is BIOS (Basic input output system).
Program: - A sequence of instructions that perform certain tasks is called Program.
User: - The person who uses the computer is called user.
Peripheral: - The input, output and storage devices which can be connected to the system cabinet are called Computer Peripherals or peripheral devices. Examples: Printer, Scanner, Card reader etc.

Assignment-1
1. Define the term computer. Compare hardware, software and firmware.

Characteristics of a computer: (5 marks)

Computer is the most useful and powerful machine which can perform various tasks. The major characteristics of computers are speed, storage, accuracy, versatility, diligence, automation, word length, non-intelligent etc.

Electronic
Speed
Storage
Accuracy
Versatility
Diligence
Automatic
Non-intelligent
Word Length

Electronic:- A computer is an electronic machine developed to perform calculations and control operations that can be expressed either in logical or numerical terms. Most computers' parts are electronic devices which are made of semiconductor chips.
Speed:- A computer can work at very high speed and is much faster than humans. One second is a very long time for a computer to perform a task. The time used by the computer to perform an operation is called the processing speed. The speed of the computer is calculated in MHz (Megahertz) , that is one million instructions per second. Today, a powerful computer can perform billions of operations in just one second.
Storage:- A computer can store a large amount of data permanently. Users can use this data at any time. We can store any form of data in a computer: text, graphics, pictures, audio and video, etc. The storage capacity of the computer is increasing rapidly. We can store data, information, etc in storage devices such as hard disk, pen drive in terms of KB, MB, GB, TB, PB, etc.
Accuracy:- Accuracy concerns the act of providing results without any error. Computers can process large amounts of data and generate error-free or, say, almost 100% error free results. A modern computer performs millions of operations in one second without any error. However, sometimes, we get wrong output due to the fault in the data, instruction or program which is known as Garbage in Garbage out (GIGO).
Versatility:- A computer can perform various types of tasks. Interestingly, the same computer can be used for various purposes Such as accounting, generating pay slip, playing games, listening to music, watching movies, typing and printing documents, sending emails, and much more.
Diligence:- Unlike human beings, a computer never feels tired or bored to do a task repeatedly for a long time. No wonder, the computer can perform the same task with the same speed and accuracy even for hours and days so long as it is provided with a suitable environment and correct program.
Automation:- Computers can be programmed to perform a series of complex tasks automatically. For that reason, the computers have been used for quality control in the industries which perform the task without getting any instructions from the operator.
Non-intelligent:- Although the computers are incredibly faster, more powerful and accurate than humans, it does not have a common sense- it can't think and decide itself to do any task.
Word Length:- Word length refers to the number of bits that the CPU can process in parallel at a time. Modern processors, including embedded systems, usually have a word length of 8, 16, 24, 32 or 64 bits, while modern general purpose computers usually use 32 or 64 bits. The power of a computer depends upon the word length. Higher the world length, better the performance of computers.

Merits and Demerits of computer

Computers have been an integral part of our daily life in this modern age. Nothing is absolute: everything has its flaws and weaknesses. And, the same applies in computers too, However, its merits weigh much heavier than demerits.

Advantages of Computer

A computer is much more reliable, fast, versatile and useful in doing repeated jobs and is less prone to data loss.
Computers can search free-text as well as structured data to find a specific data value.
Computers are the best tools when it comes to predicting to a large extent what type of results a business plan would throw up
Computer saves time and also gives error free result.
Computers provide highly accurate answers and calculations.
Using a computer, one can analyze the data and make informed decisions about the future course of action.

Disadvantages of Computer

It costs much to have computer equipment and software.
Highly-skilled IT (Information Technology) personnel is required.
Computers decrease/discourage physical activities affecting health in a major way
Software configurations do not necessarily communicate with each other.
Need repair, update and maintenance frequently.
Misunderstandings can arise quickly and be difficult and time-consuming to solve.

Assignment-2
1. List out the characterisitcs of computer.
2. List out the merits and demerits of computer.

Application of Computer

Although, the early computers were mainly used for mathematical calculations to predict impacts of bombs, path of artillery shells, calculate some other numerical values etc. With the development of technology, modern computers have played an important role in society. In modern days, computer are used in different fields, some of them are as follows:

Education:- Computers have been used in education to help the students in their study and the teachers to organize and prepare their teaching materials and collect required information from the internet. Due to the availability of eBooks in CD, DVD and on the internet, computers have been a very helpful and essential device for students and teachers for their better education.
Offices:- Modern computers are very necessary and useful resources in the office. In offices, computers are used in preparing the reports, letters, notice, salary sheet, income and expenditure reports etc. So that efficiency and work speed of the employees will be improved. Generally Microsoft Office and accounting packages are used in an office to handle the daily works.
Health and Medical field:-Computers have played a vital role in the medical field as it has been used in hospitals to help doctors, nurses and technicians to diagnose disease, getting information about patients, disease and drugs. Similarly, many computerized equipment such as CT scan machines, eye testing machines and many computerized machines are used for experiment and disease diagnosis. Surgeons also use the computerized device to get the information about the condition of the patient.
Home:-Nowadays computers are used in home to store personal records, photos, videos, playing games, listening music, watching movies etc. It can be used even to connect the internet and use services like email, chatting, online TV streaming, downloading songs and movies etc.
Bank:-Computerized technology has brought revolution in the bank. Unlike in the manual system, deposit and withdrawal became quickly in computerized banks. A computer is also used to maintain ledger, to provide the online service to the customers who need services from their home, to transfer amounts etc. For these purposes, there is a central computer called server. In banks, mostly in head offices, this stores all the necessary information centrally so that it can be accessed from any branch office of the bank. Because of this, a customer can get services from any branch of the bank.
Due to the computer with network facility, nowadays banks also provide ATM service to customers so that a customer with an ATM card can perform a cash transaction immediately with the ATM machine at any time and from any place.
Industries:-Computers have been used in industries for various purposes such as keeping the employees record, income and expenditure record, salary sheet, measurement and display of physical quantity, quality control of production etc. The different tasks which are risky for human beings are being done by computerized robots in industries so that human life will not be at risk.
Science and technology:-Since the invention of early computers, it has been a great aid for the mathematician and scientist for doing fast and correct calculation. Scientific and technological research work involves complex and massive calculations.
In many cases, simulation is also required. Such massive calculation and simulation are not possible in paper or by hand calculations. Modern computers are best for scientific research for the analysis of data.
Recording and film studio:-The modern computer can also be used for recording songs, movies and dialog. It is also used in film studies to do animation and movie production. It is used to make the movie more interesting, more popular and more attractive.
Nowadays, the music and songs can be recorded at different tracks, time and place. Similarly, movie editing also has been very easy due to the computerized system.
Weather forecasting:-Weather forecasting is not an easy task as it is done after the analysis of the images, temperature, wind speed, humidity etc. of different places, which is sent by the satellite. The analysis of these large data is not possible without the use of computers. Computers analyze the direction of the wind, cloud structure, past data and many other factors to forecast the weather. Due to the use of specific computers, we can see that BBC, CNN and other news channels predict the weather forecasting.
Reservation:- By using the computer with internet facilities, the reservation for the air ticket, train ticket, bus ticket etc. becomes possible. It also stores information regarding passengers such as name, address, age, destination, data etc. Due to the credit card and debit card facility the passengers can reserve and purchase the tickets even from their own home computer.
Military:-Since the past, computers have been used by the armed forces for testing and development of military devices like missiles, tanks and bullets etc. The pilotless fighter planes can carry missiles and drop at the pin-point area by the use of the computerized system. It also plays an important role in military communication.
Communication:-Due to the invention of the internet, modern computers are massively used for fast, reliable and cheap communication all around the world. Text, photo, animation, email, voice etc can be exchanged between two computers through the internet.
Library:-We can use computers in the library also to keep the records of books, magazines, reports, newspapers and other documents. We can keep also records of the library members with which books they have borrowed with detailed information.
Nowadays, many books are available in the digital format in the form of CDs and DVDs too. Similarly, many e-books are kept on the internet as e-library to read such e-books also, we need computers.
Desktop publishing house:-Desktop publishing house is the place where the design and publication of different materials like books, magazines, journals etc take place. Before publishing these materials, they should be designed properly. Nowadays, there are many computerized software for desktop designing and publishing which makes it very easy and efficient. Some of the desktop publishing software such as MS-Word, Adobe PageMaker and others, which is used to manipulate computer systems.

Assignment-3
1. List out the application areas of computer.

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History of Computer

The development of personal computers has taken a long period of time to extend the use of computers at present. There were not the advanced technologies in the ancient days. So it passed through several phases to become this phase in the present days.

The development of computers from ancient days to present days can be classified into the THREE Era which are as follows.

A) Mechanical Calculation Era	B) Electro- mechanical Era	C) Electronic Computers Era
Abacus Napier’s Bone Slide Rule Pascaline Stepped Reckoner Jacquard’s Loom Difference & Analytical Engine Lady Augusta Ada Tabulating Machine	Mark – I ABC	ENIAC EDVAC EDSAC UNIVAC

A) Mechanical Calculation Era:

1. Abacus

Abacus is the first calculating device.
An abacus consists of a rectangular frame containing a number of rods or beads which is divided into two unequal parts called heaven and earth.
The lower part is called, an earth consists of 5 beads and the upper part called, a heaven consists of 2 beads.
By moving the beads, it is used for counting as well as to find addition and subtraction.
A skilled abacus operator can work on addition and subtraction problems at the speed of a person equipped with a hand calculator.

2. Napier’s Bone

John Napier, a great Scottish mathematician invented” Principle of logarithm” i.e. log in 1614 AD.
Then, based on his own principle, he invented a simple device containing 10 rods made of ivory sticks marked with numbers in 1617 AD, called Napier’s Bone.
People could use it for faster multiplication and division.

3. Slide Rule

Based on the principle of John Napier, William Oughtred, an English mathematician, made a simple device called slide rule in 1624 AD.
It had multiple rulers marked with numbers in one pack.
People could use it for faster multiplication and division also.
It was still in use in the 1960’s by the NASA engineers of the Mercury, Gemini and Apollo programs which landed men on the moon.

4. Pascaline

Pascaline was invented by Blaise Pascal in 1642 AD, when he was just 19 years old.
He invented that device to help his father who was a tax collector.
It had some cogs and gears rotating in complement to each other and it could do addition and subtraction up to 8 digits only.
Multiplication and division were done by repeated addition and subtraction respectively.
Later a computer programming language was called ‘Pascal’ to honor him for his contribution in the development of computers.

5. Stepped Reckoner

Gottfried Wilhelm Von Leibniz was a great mathematician who managed to build a four function (addition, subtraction, multiplication and division) calculator in 1671 AD on the basis of Pascaline.
It could find square roots too.
Although the Stepped Reckoner employed the decimal number system, Leibniz was the first to advocate use of the binary number system which is fundamental to the operation of modern computers.

6. Jacquard’s Loom

Joseph Marie Jacquard invented Jacquard’s Loom in 1801 AD.
This Loom was the first to use a Punch Card.
Later the same Punch Card technology was used for Computer Programming.

7. Difference Engine & Analytical Engine:-

The Difference Engine was developed by Charles Babbage in 1822 AD, which was equal to the size of a room.
The Difference Engine was his first invention and it was powered by a steam.
The Difference Engine was fully automatic for mathematical calculation.
He obtained government funding for the development of Difference Engine due to the importance of numeric tables in ocean navigation.
By promoting their commercial and military navies, the British Government had managed to become the earth’s greatest empire.

Analytical Engine

Charles Babbage also designed another engine in 1833 AD, but unfortunately he was unable to complete it.
The analytical Engine contained all components as follows.

The store equivalent to memory.
The mill equivalent to CPU.
The input section using punched cards.
The output section using punched cards.

And modern computers are based on it. That’s why, for all his contribution, he is known as “father of Computer”.

8. Lady Augusta Ada

Lady Augusta Ada was the admirer and follower of Charles Babbage.
She was fascinated by the idea of Babbage.
She suggested Babbage use a binary number system for the computer program and data to be fed into the Analytical Engine on Punch Card.
She gave the concept of computer programming for the first time, so she is considered as “First Computer Programmer”.
She invented subroutine and the importance of looping.
She found that the same set of Punch Cards could be reused to repeat certain instructions.
One programming language “ADA” was named to honor her for her great contribution in computer programming.

9. Tabulating Machine

The very first census of 1790 had only required 9 months, by 1880 the U.S. population had grown so much that the count for the 1880 census took 7.5 years. Automation was clearly needed for the next census.
The census bureau offered a prize for an inventor to help with the 1890 census and this prize was won by Dr. Herman Hollerith for the development of the Tabulating Machine.
By using the similar ideas of Jacquard’s Loom he made a Tabulating Machine in 1886.
It could process on the Punch Cards and perform the census calculation faster and accurately.
Hollerith’s technique was successful and the 1890 census was completed in only 3 years at a savings of 5 million dollars.
He established his own company called Tabulating Machine Company (TMC).
Later, TMC joined with another company and established IBM in 1923 AD.
IBM is the largest computer manufacturing company in the world even today.

Assignment-4
1. List out the name of inventions along with respective inventors in mechanical era.

B) Electro- Mechanical Era

10. Mark-I

It was designed by Howard Aiken.
This was the first programmable digital computer.
This machine works on decimal not in binary format.
Its dimension was 51 feet long, 8 feet tall and 3 feet wide.
It had a 50 feet rotating shaft running its length, turned by a 5 horsepower electric motor.
It consumed a lot of electricity and emitted a lot of heat.
It was also called IBMASCC (International Business Machine Automatic Sequence Control Calculator).
This project was a joint partnership between IBM and Harvard University.
It can automatically perform a sequence of arithmetic operations: addition, subtraction, multiplications, division and table reference.
It could add or subtract two of numbers in three – tenth of a second, multiply them in four seconds.

11. ABC (Atanasoff Berry Computer)

J. V. Atanasoff was a Professor of Physics and mathematics, with the help of his graduate student Clifford Berry; he built a machine that could solve different types of mathematical problems successfully tested in 1942.
This machine was the first to store a charge on a capacitor, which is how today computers store information in their main memory (RAM).
It used 45 vacuum tubes for internal logic and capacitors for storage.

Assignment-5
1. List out the name of inventions along with respective inventors on electro-mechanical era.

C) Electronic Computer Era:

12. ENIAC(Electronic Numerical Integrator and Calculator) [1943-1946)

Dr. John W. Mauchly and John Presper Eckert developed ENIAC at the Moore School of Electrical Engineering of the University of Pennsylvania in 1946, USA.
It was the first electronic computer.
This had no moving parts except the input and output.
ENIAC was developed for military needs and was used for many years to solve ballistics (fire weapons) achieved problems.
The addition of two numbers was achieved in 200 microseconds and multiplication in 2000 microseconds.
It occupied a room measuring 9m*15 m and contained 18,000 vacuum tubes, more than 70,000 resistors, 10,000 capacitors, 60,000 switches and weighed 30 tons.

13. EDVAC (Electronic Discrete Variable Automatic Computer) [1944-1951]

It was invented by John W. Mauchly and J. Presper Eckert.
He was the first to introduce the stored program concept in a computer.
It used a binary number system rather than decimal numbers for its operation.
It had almost 6,000 vacuum tubes and 12, 000 diodes and consumed 56 KW of power.
It covered 490 square foot of floor space and weighed nearly 7 tons.
The machine requires 30 personnel to operate.
This machine ran till 1961 at a research laboratory.

14. EDSAC (Electronic Delay Storage Automatic Computer) [1947-1949]

It was invented by Maurice Wilkes at Cambridge University, England. In 1949AD.
It also used vacuum tubes.
Although, started after EDVAC, it was completed before EDVAC.
It uses a binary number system.
Both input and output used paper tape.
This machine was used to calculate a table of squares and a list of prime numbers.

15. UNIVAC (Universal Automatic Computer) [1951]

It was invented by John W. Mauchly and J. Presper Eckert.
This computer was the first commercial computer and general purpose computer produced in large quantities.
Before this, all the computers were either used for defense or census.
The UNIVAC was also the first computer to come equipped with a magnetic tape unit and was the first computer to use buffer memory.

Assignment-6
1. List out the name of inventions along with respective inventors in electronic era.

Generation of Computer:

Generation of Computer terminology is a change in technology a computer is/was being used. Initially generation of computers was used to distinguish between varying hardware technology.

There are 5 generation of computers which are as follows:

First Generation Computer(1940-1956)

The computers which were made approximately between 1940 and 1956 AD are classified as the first generation computer.
These computers had used vacuum tubes as their memory and processing devices.
Vacuum tube was developed by Lee De Forest in 1908 AD.

Characteristics of a First Generation Computer

Technology : Vacuum tube was used as its main components.
Processing Speed : Processing speed was measured in Milli-second.
Input/output Device: Punch Card was used as input / Output devices.
Computer Type : Computers were electro-mechanical.
Memory: Vacuum tube was used as a memory device.
Storage Device: First Punch cards used and later magnetic drums were used as storage devices.
Operation Mode: Computers should be set up manually as there was no operating system invented.
Reliability and Accuracy : The computers were not fully reliable and accurate.
Programming Language: Machine Level Language was used for computer programming.
Size and Cost : The size of the computer was very large and its cost was also very expensive.
Availability: The Computers were only available to the military purpose and university research.
Power Consumption and Heat Emission: Computers consumed a lot of electricity power and emitted a lot of heat
Portability: Computers were not portable because of its huge size.
Examples: ENIAC, EDVAC, UNIVAC etc.

Vacuum Tube: A vacuum tube is a hollow glass cylinder containing a positive electrode and a negative electrode between which is conducted in a full or partial vacuum tube. A grid between these electrodes controls the flow of electricity.

The major disadvantages of tubes include the fact that they require bulky power supplies and the high voltages can resent an electric shock hazard.

2) Second Generation Computer(1956-1963)

The computers which were made approximately between 1956 and 1963 AD are classified as the Second generation computer.
These computers had used transistors and diodes as their memory devices.
Transistor was invented by three scientists John Bardeen, William Shockley and Walter Brattain in 1947 AD and won the Nobel Prize in 1956 AD for it.

Characteristics of a Second Generation Computer

Technology: Transistor was used as its main components.
Processing Speed: Faster processing speed as it was measured in Micro-second.
Input/output Device: Punch Card was used as input / Output devices.
Computer Type: Computers were electro-mechanical.
Memory: : Magnetic Core (Ferrite) was used as internal memory.
Storage Device: Magnetic Tape was used as a secondary storage device.
Operation Mode: Computers should be set up manually as there was no operating system invented.
Reliability and Accuracy: These were more reliable and accurate than first generation computers.
Programming Language: Assembly and High Level Language such as FORTRAN (Formula Translation), COBOL (Common Business Oriented Language) etc. were used for computer programming.
Size and Cost: The Computers were smaller in size and less expensive than 1^st generation computers.
Availability: The Computers were available for general purpose.
Power Consumption and Heat Emission: Power consumption and Heat emission was less than 1^st generation computers.
Portability: Computers were not portable.
Examples: IBM 1401, ICL 2950 / 10, IBM 1620 etc.

Transistor: Transistor is derived from the two words “transfer” and “register” and it is the device which is made of three terminal semiconductor materials that amplifies the electrical signal or opens or closes the electronic circuit.

They were much smaller than vacuum tubes and consumed much less power. Electronic circuits could be made more complex, with more transistors switching faster than vacuum tubes.

3) Third Generation Computer(1964-Early1970's)

The computers which were made approximately between 1964 and early 1970's AD are classified as the third generation computer.
These computers had used IC (Integrated Circuit) as memory and processing devices.
The first IC was developed by Jack Kilby and Robert Noyce in 1958. Later Robert Noyce established Intel Company.

Characteristics of a Third Generation Computer

Technology: IC was used for the electronic circuit in computers.
Processing Speed: Faster than previous generation computer as processing speed was increased into Nano-Second.
Input/output Device: Keyboard and Monitor were introduced as input and output devices for the first time respectively.
Computer Type: Computers were electronic.
Memory: Semiconductor memory was used as primary memory.
Storage Device: Magnetic disk was used as a secondary storage device.
Operation Mode: Operating system was introduced for the automatic and multiprogramming.
Reliability and Accuracy: Computers became fully reliable and accurate.
Programming Language: Further development of High Level Language for Computer Programming.
Size and Cost: The computers were smaller and less expensive than previous generation computers.
Availability: The Computers were available for general purpose as well as personal purpose.
Power Consumption and Heat Emission:Power consumption and Heat emission was less than previous generation computers.
Portability: Computers became portable for the first time because of the personal or Desktop Computer.
Examples: IBM 360 Series, UNIVAC 9000, ICL 900 Series.

Integrated Circuits: ICs range from simple logic modules and amplifiers to complete microcomputers containing millions of elements. The impact of ICs on our lives has been enormous. ICs have become the principal components of almost all electronic devices. These circuits have demonstrated low cost, high reliability, low power requirements and high processing speeds compared to the vacuum tubes and transistors which preceded them.

4) Fourth Generation Computer(Early 1970's-Till date)

The computers which were made approximately between early 1970's to till now having microprocessors as CPU and VLSI (Very Large Scale Integration) are classified as fourth generation computers.
First commercial microprocessor was Intel 4004 which was made by Intel Corporation in 1971 AD.
It was a 4 bit processor because it could process only 4 bits of data at a time.
It is one of the most important generations because many achievements in the hardware and software technology took place during this generation.

Characteristics of a Fourth Generation Computer

Technology: ICs and microprocessors are used as main components with VLSI and ULSI technology.
Processing Speed: Faster than previous generation computer as processing speed was increased into Pico -Second.
Input/output Device: Input / Output devices have been further refined and invented various devices such as scanner, touch screen, printer etc.
Computer Type: Computers were electronic.
Memory: Semiconductor memory with huge capacity has been used as primary memory.
Storage Device: Use of magnetic and optical disk with large storage capacity for secondary storage devices.
Operation Mode: Multiprogramming, Multiprocessing, multimedia and distributed operating system become possible.
Reliability and Accuracy: The computers have become fully reliable and accurate.
Programming Language: Advanced HLL and 4 GL for application and database programming have been used.
Size and Cost: The computers were smaller in size and less expensive than previous generation computers.
Availability: The Computers were available for general purpose as well as special purpose.
Power Consumption and Heat Emission: Power consumption and Heat emission was less than previous generation computers.
Portability: Computers have become portable because of the development of personal or Desktop Computer, Laptop, Notebook and PDA.
Examples: IBM PC, Apple MacBook, HP 300, Acer, Dell etc.

Microprocessor: A microprocessor is a computer processor on a microchip. It is sometimes called a logic chip. It is the “engine” that goes into motion when you turn your computer on. A microprocessor is designed to perform arithmetic and logic operations that make use of small numbers – holding areas called registers. When the computer is turned on, the microprocessor is designed to get the first instruction from the BIOS that comes with the computer as part of its memory. After that, either the BIOS, or the operating system that BIOS loads into computer memory, or an application program is “driving” the microprocessor, giving it instructions to perform.

5) Fifth Generation Computer

Although the computers of this generation have not come yet in reality, computer scientists have been trying since 1990 AD.
It is said that the computer of this generation will use AI (Artificial Intelligence) and biochips as memory devices so that they can think and decide like a human being.
Biochips will be made of biological organism and protein fibers obtained from the living organism.
So, this computer will have power of sense, logic and decision making capacity.

Characteristics of a Fifth Generation Computer

These computers will have fully parallel processing capacity.
The computers will be intelligent equipped with AI.
The computers will use super conductor memory like bio-chips and Gallium Arsenide as memory device in a way to increase the speed very high.
Instead of HLL(high level language), natural languages such as English, Japanese etc. will be used fro giving instruction to the computer and making computer program.
The application of AI in fifth generation computer will also enable the expert system.
The input and output for these machines will be in the form of graphic images or speeches.
They are used in the field of medicine, treatment, planning, monitoring and so on, on a very small scale.
The language of operating system will be PROLOG,LISP etc.

Artificial Intelligence(AI): Artificial Intelligence (AI) is the area of computer science focusing on creating machines that can engage on behaviors that humans consider intelligent. The ability to create intelligent machines has intrigued humans since ancient times till today. With the advent of the computer plus 50 years of research into AI programming techniques, the dream of smart machines is coming true. Researchers are creating systems which can imitate human thought, understand speech, beat even the best human chess player, and many more feats never before seen or heard.

Assignment-7
1. Differentiate between 1G and 2G computer.
2. Differentiate between 3G and 4G.
3. What is AI?

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1.1.3 Measurement Unit of processing speed amd storage Unit

Computer Processing Speed

Second	S	1 second	Hertz(HZ)=10⁰ HZ
Millisecond	Ms	1/1,000	Kilo Hertz(KHZ)=10³ HZ
Microsecond	µs	1/1,000,000	Mega Hertz(MHZ)=10⁶HZ
Nanosecond	Ns	1/1,000,000,000	Giga Hertz(GHZ)=10⁹ HZ
Picosecond	ps	1/1,000,000,000,000	Tera Hertz(THZ)=10¹² HZ
Femtosecond	Fs	1/1,000,000,000,000,000	Penta Hertz(PHZ)=10¹⁵ HZ
Altosecond	As	1/1,000,000,000,000,000,000	Exa Hertz(EHZ)=10¹⁸ HZ

Measurement Unit Memory is measured in bytes. A byte is usually made up of 8 bits and represents one character, a letter, digit or symbol. The number of bytes that can be held is a measure of the memory and storage capacity. Bytes are usually measured in groups of kilobytes, megabytes, gigabytes and terabytes. The following chart defines each term.

0 or 1	1 Bit (Binary Digit)
4 Bits	1 Nibble
8 Bits or 2 Nibble	1 Byte
1024 Bytes	1 Kilobytes(KB)
1024 Kilobytes	1 Megabytes(MB)
1024 Megabytes	1 Gigabytes(GB)
1024 Gigabytes	1 Terabytes(TB)
1024 Terabytes	1 Petabytes(PB)
1024 Petabytes	1 Exabytes(EB)
1024 Exabytes	1 Zetabytes(ZB)

	1G	2G	3G	4G	5G
Time Period	1940-1956	1956-1963	1964-Early 1970	Early 1970-Till date	Present and Beyond
Technology	Vacuum tubes	Transistors	Integrated Circuits	Microprocessor	Bio-chips
Processing Speed	Millisecond	Microsecond	Nanosecond	Picosecond	More than Femtosecond
Memory	Vacuum Tube	Magnetic Cores	SemiConductors	Semiconductors	Super-Conductor
Storage	Magnetic Tapes/drums	Magnetic Tapes/disks	Magnetic disks	Magnetic disks/ Optical disks	Magnetic disks/ Optical disks
I/O Devices	Punch cards	Punch Cards	Keyboard/Monitor	Keyboard/Monitor/ others	Advancements in I/O
Size,cost,power consumption, heat emmision	Very high	High	High	Very low	very low
Reliability and accuracy	Not fully	more than 1G	Fully than previous	Fully than previous
Programming Language	Machine	Assembly and High Level	High Level (3G)	High Level (4G)	Natural Language
Examples	ENIAC,EDVAC	IBM 1401, IBM 1620	IBM 370 Series,PDP 11	IBM PC, Pentium PC, Apple mac Book

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Bonus

History of Computer in Nepal

It was in 2028 B.S. when HMG brought IBM 1401 (a 2^ndgeneration computer) on rent for Rs. 1 Lakhs and 25 thousand per month to process census data. It took 1 year 7 months and 15 days to process the census data.
In 2038 B.S., a 2^nd generation computer was imported with the aid of UNDP and UNFPA from England for 2 million US dollars by NCC (National Computer Center), its name was ICL 2950/10 for the National Census 2038 B.S.
ICL 2950 had 64 terminals and it is kept in the museum now.
In 2039 B.S. microcomputers such as Apple, Vector, and IBM etc were imported by private companies and individuals.
Computer Association of Nepal (CAN) was established in December 1992.
From the government of Nepal’s side, to implement IT law in the country, a draft was prepared in 2057 B.S., which was fully fledged sanctioned from 2062, Bhadra.
Now -a-days probably each and every institution, business organizations, communication centers, ticket counters etc are using computers based on the latest model and architectures as well.

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1.1.4 Classification of Computer

On the basis of Size

1. Super Computer [ 5 marks]
Super computer is physically the largest computer in size and it is the fastest, most expensive and most powerful computer. It can process large amounts of data. The fastest supercomputer can perform more than one trillion calculations per second. Some supercomputers have thousands of processors. It is especially made to process the complex and time consuming calculations. It has multiple CPUs hence it supports fully parallel processing (ability to carry out multiple operations or tasks simultaneously).

Applications of super computer in real life situation are as follows:

It can be used to forecast the weather and global climate.
It is used in military research and defense systems.
It is used in Automobile, Aircrafts and Spacecrafts designing.
It is used for encoding and decoding the sensitive information.
It is used in seismograph, plasma and nuclear research.
It is used for the study of DNA and genetic engineering.

Examples of Super Computer: CRAY-3, CYBER 205, PARAM etc.

2. Mainframe Computer It is the second largest computer which covers about 1000 sq. feet. It is a general purpose computer which has been designed for large scale data processing. It is also a very expensive and high speed computer system. It supports large numbers of computer terminals with separate input and output units in each terminal so that about 100 or more persons can work on this computer at a time. Time sharing techniques are used to access the same computer at the same time by multiple users.

Mainframe computers are used in large organizations such as insurance companies and banks, where many people frequently need to use the same data. In a traditional mainframe computer, each user accesses the mainframe resources through a device called a terminal. There are two types of terminal: a dumb terminal does not process or store data. It has simply an input output device whereas an intelligent terminal can perform some processing operations, but it usually does not have any storage.

Examples of mainframe computers: IBM's ES000, VAX 8000, CDC 6600 etc

Uses: Industries, Banking, Insurance companies, airlines, air traffic control etc

Assignment-8
1. Differentiate between super and mainframe computer.

3. Mini Computer It is the medium – sized general purpose computer which was first released in the 1960s. Minicomputer got its name because of its small size in comparison to other computers of those days. The capabilities of a minicomputer are somewhere between those of mainframe and personal computers. For this reason, minicomputers are also called midrange computers. It covers about 100 sq. ft. Its CPU can be connected to 50 terminals so that up to 50 persons can work on this computer at a time. It is used in medium size organizations and co-operation like banks, insurance companies, reservation centers etc. Examples of minicomputer: Prime series, AS/400, AP-3 etc Uses: University, Scientific Research, Industries

4. Micro Computer It is the smallest general purpose computer on the basis of size and it is called a microcomputer because it has a microprocessor as a central processing unit (CPU). Microprocessor is a small silicon chip which is made by integrating millions of components. It is also called a personal computer because it can be used only by a single person at a time. It is easy to handle so it is used in different application areas such as school, college, home, cyber etc. Microcomputers are of various types. For example: Desktop computer, Laptop Computer, Notebook, Palmtop computer, Pocket PC etc. The examples of microcomputer are IBM PC, Apple /Macintosh, Dell etc. Uses: Entertainment, Business, School, Personal etc.

Difference between Micro Computer and Super Computer:

Micro Computer	Super Computer
1. It is least powerful according to processing capabilities.	1. It is a more powerful computer.
2. It is the slowest computer in terms of processing.	2. It is a faster computer in terms of processing.
3. It is a general purpose computer.	3. It is a special purpose computer.
4. It is the smallest computer on the basis of size.	4. It is a largest computer in size.
5. It can be portable as well as non-portable.	5. It is a non-portable computer.
6. It is cheaper.	6. It is the most expensive computer.
7. It can be handled by only one person.	7. It requires numbers of experts to operate.
8. It has limited memory and storage capacity.	8. It usually contains larger memory and storage capacity.
9. It is used in office, houses.	9. It is used in weather forecasting, scientific research.
10. Example: Desktop PC, Laptop , Tablet etc.	10. Example: CRAY X-MP/24, NEC- 500, PRAM .

Types of Micro Computer

Desktop Computer A desktop computer is a personal computer that is designed to fit conveniently on the top of a typical office desk. A desktop computer typically comes in several units that are connected together during installation that may be the processor, the display monitor and the input devices -usually a keyboard and a mouse. Today, most desktop computers include a built in network interface card, a DVD-RW drive, a huge sized magnetic storage drive.

Workstation A workstation is specially designed for network environments in the LAN (Local Area Network) system. It is proposed for business or professional use. Workstations and applications designed for them are used by small engineering companies, architects,graphic designers, and any organization, department, or individual that requires a faster microprocessor, a large amount of random access memory (RAM) and special features such as high-speed graphics adapters. Like personal computers, most workstations are single-user computers. Unlike personal computers, workstations are typically linked together to form a local-area network although they can also be used as stand-alone systems.

Laptop A laptop computer is a portable personal computer light and small enough to sit on a person's lap. A laptop computer, true to its name can be powered by battery or plugged into the socket on the wall for power. The notable utility of a laptop computer is that it allows a person to travel with their computing resources. A laptop integrates most of the typical components of a desktop computer, including a display, a keyboard, a pointing device such as a touchpad (also known as a trackpad) and/or a pointing stick, and speakers into a single unit. Laptops are also sometimes called notebook computers. A notebook computer is a battery- or AC-powered personal computer generally smaller than a briefcase that can easily be transported and conveniently used in temporary spaces such as on airplanes, libraries, temporary offices and at meetings.

Palmtop True to its name, a small computer literally fits in your palm. Compared to full-size computers, palmtops are severely limited, but are practical for certain functions such as phone books and calendars. Palmtops that use a pen rather than a keyboard for input are often called hand-held computers or PDAs(Personal Digital Assistants). Because of their small size, most palmtop computers do not include disk drives. We can insert disk drives, modems, memory and other devices.

Tablet PC A tablet PC is a wireless, portable and personal computer with a touch screen interface. The tablet is typically smaller than a notebook computer but larger than a smartphone and primarily operated by touching the screen rather than using a physical keyboard. It often uses an onscreen virtual keyboard, a passive stylus pen or a digital pen. The term may also apply to a variety of form factors that differ in position of the screen with respect to a keyboard. The standard form is called slate, which does not have an integrated keyboard but may be connected to one with a wireless link or a USB port.

Smart Phone A smartphone is a mobile phone that includes advanced functionality beyond making just phone calls and sending text messages. Most smartphones have the capacity to display photos, play videos, check and send email and surf the web. Modern smartphones such as the iPhone and Android based phones can run third-party applications which provide limitless functionality. Although smartphones were initially used mostly by business users, they have now become a common choice for consumers as well.

Ultrabook An ultrabook is a category of thin and light laptop computer designed to bridge the market gap between tablets and premium notebook PCs. Ultrabooks provide more business-friendly features than tablets with portability than enterprise-class notebooks. Ultrabooks are distinct from notebooks for offering more power in the form of faster processors and additional RAM, plus better storage and larger screen coupled with long battery life, typically 8 hours plus, features that also make these laptops significantly more expensive than most notebooks.

Assignment-9
1. Distinguish betweeen mini and micro computer.
2. Describe different categories of micro computer.

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1.1.5 Mobile Computing and its Application

Mobile computing is a generic term describing one's ability to use technology while moving. In other words, a technology that allows transmission of data via a computer without having to be connected to a fixed physical link is mobile computing. Mobile voice communication and data communication is widely established throughout the world rapidly for sending and receiving data across these cellular networks. It allows users to transmit data from remote locations to other remote or fixed locations. This proves to be a solution to the biggest problem of business people on the move mobility. Many types of mobile computers have been introduced since the 1990s, including the wearable, smartphone etc.

Features (Advantages) of Mobile Computing

Portable: Mobile computing reduces transaction cost from one account to another because of portability and easy communication access.
Social interactivity: It is a very useful tool for social interactivity that allows data sharing and collaboration between users.
Context sensitivity: It is also a very useful tool for context sensitivity to gather and respond to real or simulated data unique to a current location, environment or time.
Connectivity ability: Its connectivity ability helps for communication of data in any environment.
Commonly used: It is commonly used for solving difficult activities and lesson customization for individual learners.
Quick service: We can sell a product or give service in quicker time by using mobile computing.
Easy and quick enhancement: Mobile computing is becoming very popular for streamline business processes for its quick and easy promotion and enhancement.

Technical and Other Limitations
(Disadvantages) of Mobile Computing

Insufficient bandwidth: If the user needs access to a network such as the internet on the go, they must resort to slow wireless WANs (Wide Area Network) systems primarily intended for telephone use. Higher speed wireless LANs (Local Area Network) are only available in specific sites.
Security standards: When working, mobile one is dependent on public networks, requiring careful use of VPNs (Virtual Private Network).
Power consumption: Since the grid cannot be used, mobile computers must rely entirely on battery power. Being combined with compact size, it uses unusually expensive batteries.
Human interface with device: These are still uncommon- screens are often too small. Keyboards are impractical, especially one-handed, and alternative methods such as speech or handwriting recognition require training.

Application of Mobile Computing

Arbitrary wireless network service freely helps to connect networks, and this provision enables you to access data anywhere without time and place limitation. Now is the time to discuss how various mobile computing applications help shape our future. We shall begin by slightly discussing its role in business. Efficient as it is, mobile computing is being increasingly used in diverse areas such as agriculture, education, military, transportation, disaster recovery, and medical emergency care.

Business: In different businesses, say for example, shops, malls, trade centres supermarkets, in every business, mobile computing is used. When it comes to finding out the current rate of goods, for order, delivery or payment of goods, mobile computing applications are used. CEO of any company with help of this computing system can do presentation in front of their clients, and alongside can access hot news of the market. It helps to conduct video conference and discuss on the topic at any time. It helps achieve strategic business benefits. Usually, people these days enjoy buying cinema tickets and other tickets by using mobile devices. They can access the latest market share information too. By using mobile computing, bills are easily sent to customers; it eliminates the use of paper work. Thus, with the evolution and use of mobile computing and related devices, business activities continue to speed up contributing to carn benefits in the companies.
Education: Mobile computing application is equally holding much space in the field of education too. Many companies now tend to launch mobile classrooms whereby students are able to access education material simply by using mobile devices. Many search engines have added features that help to search books, research papers and other material by using mobile devices. Nowadays, many examination results are displayed on mobile devices.
Medical: Patients these days have increased access to specialized doctors. They don't need to consult with the doctor or the hospital that is near and easy to find. They can approach the best of the best doctors, say, specialists when they are connected through the Internet. The patients can from home describe their problem to the doctors and seek out their advice. For further diagnosis, the doctor may suggest various clinical tests. In the recent decades of tele-medicine and tele-diagnosis, even the reports can be e-mailed to the doctor/patient from any place. It reduces the compulsion of doctor- patient meeting, checking and prescribing of medicine in the hospital. Then, the doctors can recommend medicine required or more suggestions if any via mobile.
Banking: Many banks now offer banking services over Internet, voice and mobile phones through SMS. All the updates of transactions are provided to the customers on their mobile devices. People now do not bother to go all the way to the banks to perform their transactions. People use plastic money (card) to perform transactions. ATMs wirelessly connected to handheld devices through Bluetooth can be used to operate in rural areas. Credit card authorization is performed on mobile POS terminals equipped with wireless adapters.
Airlines: It is used for accessing/confirming a number of things: reservation, flight schedule, flight arrival, departure information and ticketing information by busy travellers by using handheld devices. Airline baggage and cargo control is done through automated machines. Mobile computing makes it easier, faster and quicker for one to check in baggage by merely scanning the bar-coded information from baggage tickets directly into a database.
Rural area: In Rural areas, mobile computing technology would be very effective where basic infrastructure like power is either unreliable or lacking to support conventional computing technology. The government is planning facilities of m-voting, m-interaction and m-administration. M-administration is concerned with improving the operations and communications with government units The government employees can be notified about various policies from the mobile device which is sure to provide better and faster access to information. The government-citizen interaction is an approach by which interaction with the government officials is made easy and quick by use of mobile devices. Similarly, information about weather, crops diseases, time and modality of purchase of fertilizer and pesticide, the location of dealer and price, almost everything is provided to farmers via mobile devices. They are also informed about potential places for the sale of their crops. Therefore, now is the best time to use mobile devices and services. The days of writing applications and stand- in- line the whole day to ask the officer at the counter for the information are gone. It saves time, money and energy.
Defense: In the defense field, mobile computing gives high level-performance and energy- efficient solutions. Defense as such is a very sensitive matter whose facts and figures must strictly remain confidential. It provides soldiers with an access to information anytime, anywhere-thereby improving their situational awareness by use of a small, ultra-mobile device. With this device, soldiers have access to easily communicate with others to update themselves with the latest information. Not just this, many other devices are now set in fighter planes in a way to better track places and any suspicious objects around.
Traffic: During travel/ journey, if we seek to update the road situation, traffic jam, mileage and so on, mobile devices are there to give us every update for further preparedness. Similarly, digital audio broadcasting (DAB) music can refresh you while in drive. What would you do if you forgot the road/route? Simply hit your head and regret travelling or connect yourself with a road navigation device/global positioning system (GPS)? And, what if you met with an accident? Run around to inform the police and ambulance? All you need to do is to pick your mobile and by use of a device via an emergency call contact the service provider.
Emergency Situation: Mobile computing plays a vital role in the medical sector at critical hours when one must hire an ambulance. Good quality wireless connection brings you a world of help to update and pass on the significant information about injured persons. Only Wireless networks are of reliable help at the hour to update and pass on the information about natural disasters such as earthquakes, tsunami, flood and fire. Mobile computing can easily thus save life and property and alerts people for further preparedness.

Assignment 10
1. List out the features of mobile computing.
2. List out the advantages, uses and limitations of mobile computing.

1.2 Computer System and I/O devices

Definition of Computer Architecture: The design, arrangement, construction or organization of the different parts of a computer system is known as Computer architecture. It is the conceptual design and fundamental operational structure of a computer system.

Definition of Computer Organization: Computer organization refers to the operational units and their interconnections that realize the architecture specification. Computer organization deals with physical aspects of computer design, memory and their types as well as the microprocessor design.

Definition of Computer System: The integration of different computer parts such as keyboard, mouse, monitor, CPU etc to form an entire system to work effectively and efficiently is called Computer System.

1.2.2 Components of Computer System (8 marks)

A computer system refers to the fully functional system that is the integration of both hardware and software. The hardware components of a computer system are physical components that are tangible such as keywords, mouse , processor, motherboard ,main memory, secondary memory, monitor, printer etc. whereas the software components are logical components that make physical components work such as data, information ,computer instructions etc.

The major hardware components of a computer system are:

Input unit
Processor or CPU
Memory Unit or Storage
Output unit

click for figure of computer system

(i) Input Unit It accepts the data or instructions given by the user, and converts the data and instructions from man -readable to machine -readable code. Some common input devices include keyboard, mouse, scanner, punched cards, a teletypewriter, magnetic disk reader etc.

(ii) Processor / Central Processing Unit Central processing unit (CPU) is the portion of a computer system that carries out the instructions of a computer program, and is the primary element carrying out the computer's functions. The central processing unit carries out each instruction of the program in sequence to perform the basic arithmetical, logical, and input/output operations of the system. A CPU built on a single chip is called a microprocessor. Nowadays, microprocessors are also called processors.

Some of the primary components of a CPU or microprocessor are given below:

Registers
Control Unit (CU)
Arithmetic and Logic Unit (ALU)

Registers Registers are the primary memory of the computer system. They are mainly used to store the data during the time of processing inside the ALU. The Registers within the CPU are of special purpose temporary storage locations. The main types of registers are of general purpose and specific purpose register. The important register within the CPU is Program Counter(PC).

They are the fastest computer memory.
The storage capacity of the registers is small.
They are temporary memories of the computer.

Control Unit The Control Unit is the brain of the CPU itself. It is situated inside the processor, and controls overall operations and devices of the computer. There are two types of control units- the first type is called a hardwired control unit. Hardwired control units are constructed using digital circuits, once formed cannot be changed. The other type of control unit is a micro programmed control unit. A micro programmed control unit itself decodes and executes instructions by means of executing micro programs.

Functions of the Control Unit

The control unit carries out the controlling operations of the computer.
It performs data processing operations.
It sends control signals to various parts of the computer system for controlling.
It gives commands to the input data from the input unit to the memory unit, and then to the ALU.
It transforms results from the ALU to the memory unit to the output unit.
It gives command to store the data, instruction and program in memory.

Arithmetic Logic Unit (ALU)

The Arithmetic Logic Unit carries out as the name suggests Arithmetic and Logical operations on the data made available to it. Basic arithmetic functions which an ALU can carry out are an addition, subtraction, multiplication and division. The logical operation it can carry out is greater than, equal to, less than etc. Besides these operations, some processors also support operations which check if particular bits are on or otf. The main operations are summarized below.

It performs the basic arithmetical calculations such as addition, subtraction, multiplication etc.
It performs the logical operations such as comparing greater than, equal to etc.

(iii) Memory Unit or Storage

Main or Primary Memory Primary memory or main memory is a volatile memory of the computer. As soon as a computer starts, the primary memory stores all the running applications, Operating System (OS), user interface and any others. A program/application that is opened in primary memory interacts with the system processor to perform all the application specific tasks. They are directly accessible to the processor. The primary memory consists of the Random Access Memory (RAM), which can handle the instructions and data at high speed. Programs are stored in the main memory while they are being executed. Data is stored only when power supply is given to the computer.

Properties of primary memory:

It is a volatile computer memory.
The storage capacity of the primary memory is smaller than that of the secondary memory.
They are faster than the secondary memory.
They store data during the time of processing.

Auxiliary Memory or Storage Auxiliary memory is also called secondary memory. They have slower access rates for greater storage capacity and data stability. The auxiliary memory holds the programs and data for future use because it is non-volatile. The early forms of auxiliary storage included punched paper tape, punched cards, and magnetic drums. The most common forms of auxiliary storage now are of magnetic disks, flash memory, magnetic tapes, optical discs etc. The purpose of auxiliary memory is to store a large amount of data for future references.

Properties of Auxiliary or Secondary Memory:

The storage capacity of auxiliary memory is high.
They are slower because they do not directly interact with the processor.
They are less expensive.
They store data for future references.

(iv) Output Unit: When the computer completes its processing task, the result must be conveyed back to the user. The information from the CPU is converted into an understandable form through the output devices. The output of the computer can be presented into different ways such as softcopy(display from monitor) , hard copy(printed from printer) etc. Some commonly used output devices are monitor, printer, plotter, speaker etc.

Assignment 11
1. List the features of computer architecture and computer organization.
2. List the components of computer system.

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1.2.3 Microprocessor

The microprocessor is the center of the computer. It processes instructions and communicates with the outside devices, controlling most of the operation of the computer. The microprocessor usually has a large heat sink attached to it. Some microprocessors come in a package with a sink and a fan included as a part of the package. Other microprocessors require you to install the heat sink and fan separately. In the world of personal computers, the terms microprocessor and CPU are used interchangeably. At the heart of all personal computers and most workstations sits a microprocessor.

The CPU (Central Processing Unit) is the core of any computer, while the microprocessor refers to the whole functional chip that is inserted into a motherboard. The CPU is the sub architecture of the microprocessor that interprets the program instructions. Interestingly, all CPUs are microprocessors, all microprocessors are not CPUs. CPU stands for "Central Processing Unit" but it is not the only microprocessor in a modern computer system.

Functions of Microprocessor

It controls the input and output devices of a computer.
It controls the storage of data inside a computer.
It performs the arithmetical and logical operations of computers.
It processes every type of data.
It handles every other part of the computer.

Characteristics of Microprocessor

Instruction set: The set of instructions that the microprocessor can execute.
Bandwidth: The number of bits processed in a single instruction.
Clock speed: Given in megahertz (MHz), the clock speed determines how many instructions per second the processor can execute.
Word length: It depends upon the width of the internal data bus, registers, ALU, etc. An 8- bit microprocessor can process 8-bit data at a time. The word length ranges from 4 bits to 64 bits depending upon the type of the microcomputer. A processor of longer word length is more powerful and can process the data at faster speed as compared to the processor of the shorter word length

Components of Microprocessor

Types of Microprocessor

Complex Instruction Set Computer (CISC): It is a type of microprocessor design. The CISC architecture contains a large set of computer instructions that range from very simple to very complex. Intel Pentium processors are mainly CISC-based, with some RISC facilities built into them.
Reduced Instruction Set Computer (RISC): It is a microprocessor that is designed to process a small number of computer instructions so that it can operate at a higher speed (process millions of instructions per second). A larger list or set of computer instructions tends to make the microprocessor more complicated and slower in operation.

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1.2.4 Bus System (5 marks)

The components of the computer are interacted by bus. There are different types of bus structure. The bus is a medium used to transfer the data, memory address and control signal from one part to the other part of the computer.

Functions of Bus Architecture:

It carries information from one place to another.
It may carry data, address or instructions.
One component interacts with the other through the bus.

click for figure of computer BUS

Types of Bus:

Address Bus: It is a group of wires or lines that are used to transfer the addresses of Memory or I/O devices. It is unidirectional. In Intel 8085 microprocessor, Address bus was of 16 bits. This means that Microprocessor 8085 can transfer a maximum 16 bit address which means it can address 65,536 different memory locations.
Data Bus: It is used to transfer data within Microprocessor and Memory/Input or Output devices. It is bidirectional as a Microprocessor requires sending or receiving data. The word length of a processor depends on the data bus, that's why Intel 8085 is called 8 bits Microprocessor because it has an 8 bits data bus.
Control Bus: A control bus is a computer bus used by the CPU to communicate with the devices that are contained within the computer. This occurs through the physical connections such as cables or printed circuits. The CPU transmits a variety of control signals to the components and devices to transmit control signals to the CPU using the control bus. One of the main objectives of a bus is to minimize the lines for communication.

Assignment 12
1. List the functions of microprocessor.
2. What are different computer buses?

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1.2.5 Primary Memory

The computer memory is a data storing device. There are many categories of memories: primary and secondary memory. Similarly, the RAM, ROM, registers, accumulator, floppy, hard disk, CD-ROM, magnetic tapes etc are examples of computer memory. The processing capacity of a computer not only depends on the processor, but also on the capacity of the primary memory. The evolution of computers from one generation to the next generation shows the variation in the processing speed, storing capacity, reliability, power consumption, and size. A memory system can be logically divided into two categories: primary memory and secondary memory.

click for figure of computer MEMORY

The primary memory of computers is also called the main memory of computers. It is a fast and less capacity computer memory. The primary memories of computers include ROM, RAM, cache memory, registers etc. They are mainly used to store the data during the time of processing. The fast and integrated memory of less capacity is termed as primary memory or main memory. These memories have a great effect on the processing speed of computers. Some such types of memories are explained below.

Random Access Memory (RAM)

Random Access Memory (RAM) is a form of computer data storage. Today, it takes the form of integrated circuits that allow the stored data to be accessed in any order (that is, at random). The word "RAM" is often associated with the volatile types of memory, where the information is lost after the power is switched off. The advantage of using a RAM is to store whatever you're working on at any moment and the RAM is a very fast memory.

Types of RAM

Dynamic Random Access Memory (DRAM): It is a type of random-access memory that stores each bit of data in a separate capacitor within an integrated circuit. The capacitor can be either charged or discharged; these two states are taken to represent the two values of a bit, conventionally called 0 and 1. Since the real capacitors leak charge, the information eventually fades unless the capacitor charge is refreshed periodically.
Static Random Access Memory (SRAM): It is a type of semiconductor memory where the word static indicates that, unlike dynamic RAM (DRAM), it does not need to be periodically refreshed. It is still volatile in the conventional sense that the data is eventually lost when the memory is not powered.
SRAM is more expensive, but faster and significantly less power consuming than DRAM. It is, therefore, used where either bandwidth or low power, or both, are principal considerations. SRAM is also easier to control. SRAM is less dense than DRAM and is, therefore, not used for high-capacity, low-cost applications such as the main memory in personal computers.

Differences between SRAM and DRAM

SRAM	DRAM
(i) SRAM stores data or programs as long as the power supply is ‘ON’ state.	(i) DRAM loses its stored information in a very short time (few milliseconds) even though the power supply is ‘ON’ state.
(ii) It doesn’t require a refreshing circuit.	(ii) It needs to be refreshed periodically so as to retain data or programs stored in RAM, so a refreshing circuit is needed.
(iii) It has a higher speed compared to DRAM.	(iii) It has a lower speed than SRAM.
(iv) It stores data in a flip-flop circuit containing transistors in a memory cell.	(iv) It requires less number of transistors per memory cell because capacitors and one transistor are needed to form a memory cell.
(v) It stores bit as voltage.	(v) It stores bit as a charge.
(vi) It is expensive in cost.	(vi) It is cheaper in cost.
(vii) The memory cell of SRAM is larger in size and loosely packed.	(vii) The memory cell of DRAM is smaller in size and is tightly packed.
(viii) It is usually available in a smaller storage capacity of a few MB.	(viii) It is usually available in a large storage capacity of a few GB.

Read Only Memory (ROM)

It is a class of storage media used in computers. The data stored in the ROM cannot be modified, or can be modified only slowly or with difficulty; therefore, it is mainly used to distribute firmware. The manufacturing company already installed the program in the ROM.

Types of ROM

Programmable Read Only Memory (PROM): Programmable read-only memory (PROM), or one time programmable ROM (OTP), can be written to or programmed via a special device called a PROM programmer. Typically, this device uses high voltages to permanently destroy or create internal links within the chip. Consequently, a PROM can only be programmed once.
Erasable Programmable Read Only Memory (EPROM): Erasable programmable read- only memory (EPROM) can be erased by an exposure to the strong ultraviolet light (typically for 10 minutes or longer), then rewritten with a process that again needs higher than usual voltage applied. Repeated exposure to the UV light will eventually wear out an EPROM.
Electrically Erasable Programmable Read Only Memory (EEPROM): Electrically erasable programmable read-only memory (EEPROM) is based on a similar semiconductor structure to EPROM; however, it allows its entire contents to be electrically erased, then rewritten electrically, so that they need not be removed from the computer.

Difference between RAM and ROM (Important Question)

RAM	ROM
(i) RAM stands for Random Access Memory.	(i) ROM stands for Read Only Memory.
(ii) It allows both read and write operations.	(ii) It allows only reading operation.
(iii) It is volatile in nature i.e. data is lost when the power supply is switched off.	(iii) It is non-volatile in nature and used for permanent storage.
(iv) It is used when an IO operation is performed, known as buffering.	(iv) It is not used for buffering purposes.
(v) It usually has a higher memory space than ROM.	(v) It usually has less memory space than RAM.
(vi) The second operation after booting the computer system is performed in RAM.	(vi) The first operation in the computer system is performed in ROM(during the booting process)
(vii) It is used to store data/information while they are being processed, waiting to be processed, and after being processed before it is provided to the output component.	(vii) It is used to store programs that are required for the operation of electronic devices.
(viii) It is usually expensive on a per unit basis while compared on the basis of storage capacity RAM is cheaper.	(viii) It is usually cheaper in terms of per unit basis but while comparing on the basis of storage capacity ROM is expensive.
(ix) Types of RAM are SRAM and DRAM.	(ix) Types of ROM are PROM, EPROM and EEPROM.

Assignment-13
1. What is computer memory? Prepare a list of defferent types of computer memory.
2. What is primary memory? Prepare a list of different types of primary memory.
3. Differentiate between RAM and ROM.

Cache Memory

Cache memory is an extremely fast memory that is built into a computer's central processing unit (CPU), or located next to it on a separate chip. The CPU uses cache memory to store the instructions that are repeatedly required to run the programs and improve the overall system speed. The advantage of cache memory is that the CPU does not have to use the motherboard's system bus for data transfer. Whenever data must be passed through the system bus, the data transfer speed slows to the motherboard's capability. The CPU can process data much faster by avoiding the bottleneck created by the system bus.

Cache memory is a temporary memory that a computer microprocessor can access more quickly than it can access the regular RAM. As the microprocessor processes the data, it looks first in the cache memory, and if it finds the data there (from a previous reading of data), it does not have to do the more time-consuming reading of the data from large memory. There are two processes in cache: cache hit and cache miss.

Cache Hit: At first, the processor sends the address of the desired data to the cache, if the data is available, then, the event is called - Cache hit.
Cache Miss : When the address sent by the processor is not present in the cache, the event is called cache miss. After the cache miss, the data of the main memory is copied to the cache for the next cache hit.

Features of Cache Memory

It is a temporary memory.
It is a small size memory.
It is a fast memory.
It increases the speed of a computer.
Its internal cache is inside the microprocessor and the external caches are outside the microprocessor

L1 and L2 Cache

L1 and L2 are the levels of the cache memory in a computer. If the computer processor can find the data it needs for its next operation in cache memory, it will save time compared to having to get it from the Random Access Memory(RAM). L1 is "Level-1” cache memory, usually built onto the microprocessor chip itself. For example, Intel MMX microprocessor comes with 32 thousand bytes of L1. L2 (that is , Level-2) cache memory is on a separate chip(possibly on an expansion card) that can be accessed more quickly than the larger “main” memory. A popular L2 cache memory size is in terms of megabytes.

Buffer

It is a memory that is used in a portable computer. It is used to store more than one piece of data. It lies between the I/O devices and the CPU. It is used to hold the data prior to being used by the CPU. Buffered memory is a type of computer memory. It is designed to control the amount of electrical current which goes to and from the memory chips at any one time. This makes for more stable memory, but increases the cost and slows the speed at which it works.

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1.2.6 Secondary Memory

Secondary memory, also known as secondary storage, is a slower and cheaper form of memory. The CPU does not access the secondary memory directly. The content in it must first be copied into the primary storage RAM for the CPU to process. The secondary memory devices include the hard drives, floppy disks, CDs and CDROMs etc. The secondary memory is where the programs and the data are kept on a long-term basis.

Differences between Primary Memory and Secondary Memory[2076 Set C]

Primary Memory	Secondary Memory
1. It is also called main, internal, or system memory.	1. It is also called as auxiliary, external or backup memory.
2. It holds data,program, and information which are currently under execution.	2. It holds data,programs and information permanently.
3. It is directly accessible to the CPU.	3. It is not directly accessible to the CPU. It requires primary memory for its operation.
4. It is usually volatile memory except for ROM.	4. It is a non-volatile memory in nature.
5. It can not be used for carrying data from one computer to another.	5. It can be used to transfer data from one computer to another.
6. It is usually an expensive per bit cost.	6. It is usually cheaper per bit cost.
7. It is faster to read/write operations.	7. It is slower to read/write operations.
8. It is used in smaller storage capacity in PCs.	8. It is used in larger storage capacity in PCs.
9. It is normally made with semiconductor material and is in the form of IC(Chip).	9. It can be magnetic, optical or semiconductor memory and is normally in the form of a disk.
10. It is on the top level of the memory hierarchy.	10. It is on the low level of the memory hierarchy.
11. It is on board memory(internal),i.e. It is part of the motherboard.	11. It is the external media and attached to the motherboard as a separate device.
12. Examples of primary memory are RAM, ROM, Cache Memory etc.	12. Examples of secondary memory are Hard disk, CD,DVD, Pen Drive etc.

Assignment-14
1. What is cache memory.
2. Differentiate between the primary and secondary memory of a computer.

Magnetic Disk

Magnetic disk is the most widely used storage medium for computers. A magnetic disk offers high storage capacity, reliability and fast to access the data. It accesses the data randomly. Magnetic disks are flat circular plates of metal or plastic, coated on both sides with iron oxide. The types of magnetic disk are hard disk, floppy disk etc.

Hard Disk

In any computer system, the hard disk is considered as the secondary memory device. The primary memory is obviously the RAM. But as the RAM is the primary memory, it cannot be used for the purpose of permanent data storage. Hence, a secondary memory device is necessarily needed for the purpose of the data storage in any computer system. The hard disk drive is the most popularly used secondary memory device. The main reason for this is the access speed and reliability of the data it can offer. In the case of the tape drives, the access speed is much lower and the data transfer is comparatively lower than the hard disk drive. The information that is required to boot a computer is stored in the hard disk boot sector. Also the importance of the hard disk drive is to store the backup of the data or any information that is created by the user. The hard disk specification should also match the expectations of the computers, that is the storage capacity and access speed. The internal organization of any hard disk drive consists of four parts, primarily: the Platters, the Head Arm, the Chassis, and also the Head Actuator. The hard disk drives are also available in two different types : the internal and also the external hard disk drives. The internal hard disk drives are used for the storage of the data in the computer case. They are not portable, and are usually inside the case. The external hard disk drives are portable, and therefore, can be connected to other computer systems as well. There is a hard casing over the hard disk. The platters are rotated at very high speed varying from 3,000 RPM (Revolution per minute) to 15,000 RPM. Information is written to, and read from a platter as it rotates past devices called read-and-write heads. The read-and-write head is used to detect and modify the magnetization of the material immediately under it. The hard disk is a non-volatile and random memory of a computer system. The hard disk has enormous storage capacity compared to the main memory. The hard disk is usually contained in the systems unit of a computer. The hard disk is used for long-term storage of the programs and the data. The data and the programs on the hard disk are organized into files-named sections of the disk. A hard disk has a storage capacity in terms of gigabyte such as 20GB, 40GB, 80GB, 320GB and more.

Advantages of Hard disk

It can store a huge amount of data in terms of megabyte to gigabytes.
External hard disks are portable. Hence, they can be used to transfer the data from one computer to another computer.
The data access time is less compared to the other secondary devices such as floppy disk, magnetic tape etc.
It stores the data safely in comparison to other devices.
It is protected from dust, fires, heat etc.

Floppy Disk

Floppy disks are mostly used for transferring software between computers. They have low capacity, and are very slow compared to the other storage devices. Floppy disks are small, removable, media storage devices. They record data onto a thin, circular magnetic film encased in a flat square plastic jacket. Floppy disks are somewhat antiquated, having been replaced by other memory devices. Floppy disks are portable magnetic storage devices. Floppy disks are not as fast as hard disk drives, nor do they store information as much. They are mainly used in moving data from one computer to the other. Floppy disks are also referred to as floppies and diskettes. Floppy disks have almost completely been replaced by CD's, DVD's.

Flash Memory Flash memory is non-volatile data storage and thus is capable of retaining its data even when its power source has been turned off. Able to retain data even when power is lost, you can rest assured that all your pictures will still be safe on the flash memory. Flash memory is a small fast, lightweight device which makes no noise while in use. Flash memory is reliable and allows you to specify which data you want to keep.

Pen Drive Pen drive is a portable USB (Universal Serial Bus) flash memory device that can be used to transfer audio, video, and data files from one computer to another computer. It is a portable device just like an external hard disk USB flash drives are called thumb drive, jump drive, pen drive, key drive, tokens, USB drive and so on. The storage capacity of pen drive is GB to TB.

Memory Card A memory card (often called flash memory card or a storage card) is a small storage medium used to store the data such as text, pictures, audio and video, for use on small, portable or remote computing devices. It is a non-volatile memory, which means that the data is stable on the memory card by a loss of power source, and does not even need to be periodically refreshed. Because memory cards are solid state media, they have no moving parts, and therefore, are unlikely to suffer mechanical difficulties. Memory cards offer a number of advantages over the hard disk drive; they're much smaller and lighter, extremely portable, completely silent, allow more immediate access, and less prone to mechanical damage. The storage capacity is from MB to GB. They are commonly used in many electronic devices, including digital cameras, mobile phone, laptop computers, MP3 players and video game consoles. They are small, re-recordable and can retain data without power.

Magnetic Tape A magnetic tape is a sequential storage device of a computer. It is no longer a common storage device these days. It is so because it is mainly used in mainframe computers and supercomputers. It is slow and sequential flow of data. It is very useful for storing huge volumes of data economically. A magnetic tape is a continuous trip of plastic. It is coated with magnetic oxide which can be magnetized to record the information as a series of magnetized/non magnetized spots to represent binary zeros and ones. Extracting information from a file is known as reading.

Advantages of Magnetic Tape

It is cheaper.
The data from magnetic tape is directly transferred into the hard disk.
The data stored on magnetic tape are of long term retrieval purpose.
It can be reused.

Disadvantages of Magnetic Tape

It is a sequential storage device.
The data access time of magnetic tape is slow.

Assignment-15
1. What is magnetic disk?
2. List the features of hard disk.

Optical Disk

An optical disk is an electronic data storage medium that can be written to and read using a low powered laser beam. It is mainly used for music, movies and software programs. It is compact, lightweight and durable. Optical disks are CD, DVD etc.

CD-ROM A CD-ROM is a compact disk Read-only memory. CD-ROMS are popularly used to distribute computer software, including games and multimedia applications, though any data can be stored. Today's mass produced CD-ROM drives are faster and cheaper than they've ever been. Consequently, not only is a vast range of software now routinely delivered on CD-ROM, but many programs are also run directly from them. The diameter of a CD ROM is 12cm, thickness of 1mm and weight of 18gm. The storage capacity of CD ROM is 650MB. It is used for read only purposes in computer systems.

CD-RW

A CD-RW (Compact Disc-Rewritable) is a rewritable optical disc. The CD-RW discs require more sensitive laser optics. Like regular CDs, CD-Rs and the CD-RWs are composed of a polycarbonate plastic, a thin reflective metal coating and a protective outer coating. The CD-R is a write once and read many formats, in which a layer of organic polymer dye between the polycarbonate and metal layers serves as the recording medium. The composition of the dye is light permanently transformed by exposure to a specific frequency of light. In a CD-RW, the dye is replaced with an alloy that can change back and forth from a crystalline form when exposed to a particular light, through a technology called optical phase change. The patterns created are less distinct than those of other CD formats. requiring a more sensitive device for playback.

CD-R

CD-R stands for CD-Recordable. It is a writable disc and drive that is capable of having information written to the disc once and then having that disc read many times after that. If the data is not written to the disc properly, it has errors, or has the incorrect information that disc or portions of that disc cannot be erased. A CD-R disc is coated with a photosensitive organic dye that allows a user to record information.

DVD

DVD is an optical disc storage media format. The DVD discs offer higher storage capacity. The DVD discs are used in DVD-Video consumer digital video format and in DVD-Audio consumer digital audio format. The DVD discs containing other types of information may be referred to as DVD data discs. It can store any types of data such as text, graphics, audio, video etc. The types of DVD are DVD-R ,DVD-ROM, DVD-R/W.

Blu-ray Disc

Blu-ray is also known as Blu-ray Disc (BD). It was developed to enable recording rewriting and playback of high definition video (HD), as well as storing large amounts of data. It offers more than five times the storage capacity of traditional DVDs and can also hold up to 25GB on a single layer disc and 50GB on a dual-layer disc. This extra capacity combined with the use of advanced video and audio codec will offer consumers an unprecedented HD experience.

Other External Storage Device

External Hard Disk

It is a hard disk that is connected outside from a computer. External hard disks are used in addition to internal hard drives in order to store more data. They are portable i.e. carry from one computer to another computer. The external hard drive is connected to the computer via an interface cable, which allows the external hard drive to communicate with the computer so that data can be passed back and forth.

Difference between Magnetic Memory and Optical Memory

Magnetic Memory	Optical Memory
i. It stores data in magnetic form.	i. It stores data optically.
ii. It is affected by the magnetic field.	ii. It is not affected by the magnetic field.
iii. It has high storage capacity.	iii. It has less storage than a hard disk.
iv. It does not use a laser beam to read/write.	iv. It uses a laser beam to read/write.
v. Magnetic storage devices are hard disk, floppy disk etc.	v. Optical storage devices are CD,DVD etc.

Memo Stick (Memory Stick)

The Memo Stick A memory stick is a removable flash memory card developed by Sony in October, 1998. It is popularly known as Memo Stick. It is a small device that connects to a computer and allows you to store and copy information. Sony promoted the Memory Stick as a new way to share and transfer images, sound recordings and other data between various electronic devices such as digital cameras, camcorders, handy cams, and Play Stations. The capacity of Memory Sticks ranges in size from 4 MB to 256 GB with a theoretical maximum capacity of 2 TB. They are smaller than comparable devices for data storage, such as smart media or compact flash memory cards. Memory Stick Pro-HG Duo HX (MSHX series) helps to save images, videos and gaming progress. It has a minimum of 15MB/s writing speed. The main use of the memory stick is for storage of media for portable devices. The Sony digital compact camera uses a memory stick to store images. A user can copy the images stored in the Sony digital camera to a computer by using a memory stick-capable memory card reader. They usually add this memory stick reader hardware to most of their electronic products such as digital cameras, digital music players, cellular phones, PlayStation Portable, etc. The difference between flash drive and memory stick is that the flash drive is an ultra-portable storage device with an integrated USB interface while the memory stick is a portable flash memory storage device used with handheld devices.

Assignment-16
1. List the properties of magnetic disk and optical disk.
2. Differentiate between CD ROM and CD RW.
3. What is a memory stick?

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1.2.7 Input Devices

Input unit consists of several input devices. It is used to provide data to the computer for processing. There are various input devices used in computer systems such as keyboard, mouse, MICR, OCR, trackball etc.

Keyboard

The keyboard was one of the first peripherals to be used with computers. It is still the primary input device for entering text and numbers. The keyboard is used to type information into the computer or input information. Numeric keyboards contain only numbers, mathematical symbols for addition, subtraction, multiplication and division, a decimal point, and several function keys. They are often used to facilitate data entry with smaller keyboards that do not have a numeric keypad, commonly those of laptop computers.These keys are collectively known numeric pad, numeric keys, or a numeric keypad, and it can consist different types of keys such as symbols, numeric digits, cursor arrow keys, navigation keys, functional keys and separate numeric key.

The most common layout of the keyboard is the QWERTY. It is named so because the first six keys on the top row of letters are Q, W, E, R, T, Y. Portable computers such as laptops quite often have custom keyboards that have slightly different key arrangements than standard keyboards.

At its essence, a keyboard is a series of switches connected to a small keyboard microprocessor that monitors the state of each switch and initiates a specific response to a change in that state. When a user presses a key, it causes a change in the amount of current flowing through the circuit associated specifically with that key. The keyboard microprocessor detects this change in current flow. By doing this, the processor can tell when a key has been pressed and when it is being released. Depending upon which key's circuit carries a signal to the microprocessor, the processor generates the associative code, known as scan code, of the key and sends it to the operating system. A copy of this code is also stored in the keyboard's memory. When the operating system reads the scan code, it informs the same to the keyboard and the scan code stored in the keyboard's memory is then erased.

According to keys keyboard are again classified by:

XT (Extended keyboard): 85 keys
AT (Advanced keyboard): 101 keys
Enhanced keyboard: 103 or more keys

Mouse

Today, most modern computers are run using a mouse controlled pointer. Generally, if the mouse has three buttons the left one is used to select objects and text and the right one is used to access menus. If the mouse has one button it controls all the activity and a mouse with a third button can be used by specific software programs.

Type of Mouse

Mechanical mouse
Optical mouse

One type of mouse has a round ball under the bottom of the mouse that rolls and turns by wheels which control the direction of the pointer on the screen. This is called a mechanical mouse. Another type of mouse uses an optical system to track the movement of the mouse, using LEDs (Light Emitting Diodes) and photo detectors. This is called an optical mouse. Laptop computers use touch pads, buttons and other devices to control the pointer. Handheld use a combination of devices to control the pointer, including touch screens.

Scanner

Scanner is a device that optically scans images, printed text, handwriting, or an object and converts it to a digital image. Scanners use a light beam to scan the input data. If the data to be scanned is an image, it can be changed by using the special image editing software. If an image is a page of text, then the special optical character recognition software must be used to convert the images of letters in text and this can be edited by using a word processor. The two most common types of scanners are hand-held scanner and flat-bed scanner. In hand-held scanners, the device is moved by hand, and has evolved from text scanning "wands" to 3D scanners used for industrial design, reverse engineering, test and measurement, orthotics, gaming and other applications. In a flat- bed scanner, the document is placed on a glass window for scanning.

Joystick

A joystick is an input device consisting of a stick that pivots on a base and reports and moves in all directions and controls the movement of a pointer or some other display symbol. A joystick is similar to a mouse, except that with a mouse the cursor stops moving as soon as you stop moving the mouse. With a joystick, the pointer continues moving in the direction the joystick is pointing. To stop the pointer, you must return the joystick to its upright position. Most joysticks include two buttons called triggers. Joysticks are used mostly for computer games, but they are also used occasionally for Computer Aided Design (CAD) and Computer Aided Manufacturing (CAM) systems and other applications. The joystick has been the principal flight control in the cockpit of many aircraft, particularly military fast jets, either as a center stick or side-stick. Joysticks are also used for controlling machines such as cranes, trucks, underwater unmanned vehicles, wheelchairs, surveillance cameras and zero turning radius lawn mowers.

Joystick elements: 1. Stick; 2. Base; 3. Trigger; 4. Extra buttons; 5. Autofire switch; 6. Throttle; 7. Hat Switch (POV Hat); 8. Suction Cup

Light Pen

A light pen is a computer input device in the form of a light-sensitive used in conjunction with a computer's CRT TV set or monitor. It allows the user to point to displayed objects, or draw on the screen, in a similar way to a touch screen but with greater positional accuracy, A light pen can work with any CRT-based display, but not with LCD screens projectors and other display devices.

A light pen is fairly simple to implement. Just like a light gun, a light pen works by sensing the sudden small change in brightness of a point on the screen when the electron gun refreshes that spot. By noting exactly where the scanning has reached at that moment, the X, Y position of the pen can be resolved. The main disadvantages of a light pen is: sometimes, it gives false reading due to background light and it cannot read completely dark spots.

Magnetic Ink Character Recognition (MICR)

Magnetic Ink Character Recognition, or MICR, is a character recognition technology used primarily by the banking industry to facilitate the processing of cheques. The technology allows computers to read information (such as account numbers) of printed documents. Unlike barcodes or similar technologies, however, MICR codes can be easily read by humans. MICR characters are printed in special typefaces with a magnetic ink or toner, usually containing iron oxide. As a machine decodes the MICR text, it first magnetizes the characters in the plane of the paper. Then the characters are passed over a MICR read head, a device similar to the playback head of a tape recorder. As each character passes over the head it produces a unique waveform that can be easily identified by the system.

Optical Mark Recognition (OMR)

Optical Mark Recognition (OMR) is the process of detecting the presence of intended marked responses. A mark registers significantly less light than the surrounding paper. Optical mark reading is done by a special device known as optical mark reader. In order to be detected by the OMR reader, a mark has to be positioned correctly on the paper and should be significantly darker than the surrounding paper. The OMR technology enables a high speed reading of large quantities of data and transferring this data to the computer without using a keyboard. The OMR reader scans the form, detects the presence of marks and passes this information to the computer for processing by application software. In this method, special printed forms / documents are printed with boxes, which can be marked with dark pencil or ink. These forms are then passed under a light source and the presence of dark ink is transformed into electric pulses, which are transmitted to the computer. It is mainly used to read the answer sheet of multiple choice questions, survey form, polling, voting application etc.

Optical Character Recognition (OCR)

Optical character recognition (OCR) is the mechanical or electronic translation of scanned images of handwritten, typewritten or printed text into machine-encoded text. It is widely used to convert books and documents into electronic files, to computerize a record-keeping system in an office, or to publish the text on a website. OCR makes it possible to edit the text, search for a word or phrase, store it more compactly, display or print a copy free of scanning artifacts, and apply techniques such as machine translation, text-to- speech and text mining to it. OCR is a field of research in pattern recognition, artificial intelligence and computer vision.

Barcode Reader

A barcode is a group of vertical bars randomly generated by computer software with different thickness and spacing. It consists of twelve digits, first six digits represent the product information and second six digits represent manufacturer details. Moreover, a separate single digit is also used for check digit.

A barcode reader is an electronic device for reading printed barcodes. Like a flatbed scanner, it consists of a light source, a lens and a light sensor translating optical impulses into electrical ones. Additionally, nearly all barcode readers contain decoder circuitry analyzing the barcode's image data provided by the sensor and sending the barcode's content to the scanner's output port. It is mostly used in supermarkets, library, bookshop, cinema hall.

Digital Camera

A digital camera is a camera that takes video or still photographs, or both, digitally by recording images via an electronic image sensor. Most 21st century cameras are digital. A digital camera uses photosensitive devices such as Charged Coupled Device (CCD) to digitize the images.

Digital cameras can do things film cameras cannot display images on a screen immediately after they are recorded. It stores thousands of images on a single small memory device, and deleting images to free storage space. The majority, including most compact cameras, can record moving video with sound as well as still photographs.

Touch Screen

The touch screen is a modern and advanced technology applied in wrist watch, camera, pager etc. It is a screen with touch sensitive points or program icons. When a specific point or icon is touched by finger tips, related programs or prompts are activated. It is normally used when information has to be accessed with minimum effort. However, it is not suitable for input of large amounts of data. Typically, they are used in information-providing systems like the hospitals, airlines and railway counters, ATM machines etc. Mainly, it is divided into two categories: optic touch screen that uses Light Emitting Diode (LED) and sonic touch screen that uses high speed sound wave on the surface of screen.

Touchpad

A touch pad is a device for pointing (controlling input positioning) on a computer display screen which is used to select the screen position and icons on the screen and give commands. It looks like a small gray window, about two inches wide. A touch pad works by sensing the user's finger movement and downward pressure. Originally incorporated in laptop computers, touch pads are also being made for use with desktop computers. Nowadays, it is commonly used in laptops, notebooks, PDA etc.

Trackball

Trackball is another pointing device that resembles a ball nestled in a square cradle and serves as an alternative to the mouse. It has a ball, which can be rotated by fingers in any direction, the cursor moves accordingly. The size of the ball of trackball varies from as large as a cue ball, to as small as a marble. Since it is a static device rather than rolling the mouse on the top of the table, the ball on the top is moved by using fingers, thumbs, and palms. The three shapes, which are commonly used, are a ball, a button and a square.

Smart Card

A small electronic device, similar to a credit card which contains electronic memory and possibly an embedded integrated circuit (IC). Smart cards containing an IC are sometimes called Integrated Circuit Cards (ICCs). Smart cards are used for a variety of purposes, including storing a patient's medical records, storing digital cash, generating network IDs (similar to a token). To use a smart card, either to pull information from it or add data to it, we need a smart card reader, a small device into which we insert the smart card. Smart cards can provide identification, authentication, data storage and application processing. Smart cards may provide strong security authentication for single sign-on (SSO) within large organizations.

Microphone

It is an input device for modern computer systems. It is used for recording voice and sound. It is mainly used for voice mail, video chat, conferencing etc. Sometimes it is also called mike or mic. Besides in computer systems, it is also used in many other systems such as telephones, tape recording, motion picture production, radio and television broadcasting etc.

Output Devices

An output device helps to give the final result from the CPU to the monitor or printer. Generally output devices are classified into two types hard copy output devices such as printers, plotter and soft copy output devices such as monitor, projector, speaker etc.

Monitor

Monitors are output devices of computers. Monitors are used to display any type of data from the computer. They are soft copy output devices. There are different types of monitors such as LCD, CRT etc. Some are explained below.

CRT Monitor

CRT stands for cathode ray tube, describing the technology inside an analog computer monitor or television set. The CRT monitor creates a picture out of many rows or lines of tiny colored dots. The more lines of dots per inch, the higher and clearer the resolution. Therefore 1024 x 768 resolutions will be sharper than 800 x 600 resolutions because the former uses more lines creating a denser, more detailed picture. Higher resolutions are important for displaying the subtle detail of graphics. For text, resolution isn't as critical. Different types of display cards are given below.

MDA - Monochrome Display Adaptor.
MCGA - Multi Color Graphic Adaptor
EGA - Enhanced Graphic Adaptor
CGA - Colored Graphics Adaptor
VGA - Video Graphics Array
SVGA - Super Video Graphics Array

Some Terms of Monitor

Phosphor:

The number, characters, and symbols, and images displayed on monitors are patterns of lighted phosphor dots. There are many types of phosphor dots used for display. In black and white TV screen P4 Phosphor is used. The phosphor is classified as P1,P4,P7 etc.

Shadow Mask

Shadow Mask is a thin metal plate placed between phosphor coating and electron guns of colour monitors. It contains tiny holes, through which electrons emitted from three electrons guns pass and strike phosphor dots to produce color effects.

Electron Guns

There are three electron guns used in color monitors each for one primary color. We know that red, green and blue are primary colors and its appropriate proportions produce several color combinations.

Pixel or Picture Elements

It is a unit of presentation. It is made up of red, green and blue phosphor dots. Pixels are very tiny dots, arranged together in rows and columns, appear continuous when in-groups.

Dot Pitch

The measurement of quality of display is resolution and dot pitch. The distance between centers of two pixels is called dot-pitch and its small value indicates sharpness of images. Its value varies 0.22 mm to 0.39 mm.

Resolution

The resolution of display depends on screen size, dot pitch and display adapter. The display adapter is a circuit board to accept formatted information from the CPU and to draw images on a monitor. The number of pixels per centimeter that can be plotted horizontally and vertically is called resolution. Colour monitors have VGA, SVGA cards to support graphics display and colors.

How does CRT Monitor Work?

An electron beam produced at the cathode is accelerated and focused to strike on the screen. The screen is covered with phosphor dots which can emit light of specific colours when excited. The three kinds of phosphor used for the dots emit red, green or blue light respectively when struck by an electron beam. Red, green and blue are called the primary colours and by combining light of these three colours at the correct ratio, all other colours (composite colours) can be produced.

To generate an image on the screen, the electron beam scans across the phosphor dot according to the information taken from the video signals. The phosphor dots at each position on the screen light up with the correct colour and intensity to create the desired image.

Advantages

It has high Refresh Rates.
It has colour Clarity and Depth

Disadvantages

It is very heavy and large.
It uses a large amount of energy.
It generates Excess Heat.

Liquid Crystal Display (LCD) Monitor

Liquid crystal display (LCD) is a thin, flat electronic visual display that uses the light modulating properties of liquid crystals (LCs). LCs does not emit light directly.

They are used in a wide range of applications, including Computer monitors, television, instrument panels, aircraft cockpit displays, signage etc. They are common in consumer devices such as video players, gaming devices, clocks, watches, calculators, and telephones. LCDs have displaced cathode ray tube (CRT) displays in most applications. They are usually more compact, lightweight, portable, less expensive, more reliable, and easier on the eyes. They are available in a wider range of screen sizes than CRT and plasma displays.

Advantages

It is smaller and lighter.
It has less power consumption.

Disadvantages

It has motion blur on Fast Moving Images.
Some models have reduced colour clarity.

Comparison between CRT and LCD

CRTs are big and bulky while LCDs are thin and light.
CRTs consume more power compared to LCDs.
A by-product of the power consumption, CRTs also get much hotter compared to LCDs.
LCDs have a greater response time than CRTs.
LCDs are considerably more expensive than CRTSs.
LCDs have more applications than CRTs.
LCDS can suffer from dead pixels while CRTS do not.

Light Emitting Diode (LED) Monitor

A Light Emitting Diode (LED) is a semiconductor device that emits visible light when an electric current passes through it. The chip has two regions separated by junction. The p region is dominated by positive charges, and n region is dominated by negative charge. The junction acts as a barrier to the flow of electrons between the p and n region. Only when sufficient voltage is applied to the semiconductor chip, current flow, and electrons cross the junction into the p region. The light is not particularly bright, but in most LEDs monochromatic, occurring a single wavelength. The output from a LED can range from red (wavelength 700 nanometers) to blue violet (400 nanometers).

Plasma Display

A plasma display panel (PDP) is a type of flat panel display common to large computer and TV displays 30 inches (76 cm) or larger. They are called "plasma" displays because the technology utilizes small cells containing electrically charged ionized gases, or what are in essence chambers more commonly known as fluorescent lamps.

A plasma display is a computer video display in which each pixel on the screen is illuminated by a tiny bit of plasma or charged gas, somewhat like a tiny neon light. Plasma displays are thinner than cathode ray tube (CRT) displays and brighter than liquid crystal displays (LCD). Plasma displays are sometimes marketed as “thin-panel” displays and can be used to display either analog video signals or display modes digital computer input.

Printer

A printer is an output device that produces text and graphics on paper. Printer is an output device used to produce hard copy information. The price of a printer depends on output quality, speed and printing technology employed. The printer is divided on the two backgrounds:

(a) On the basis of printing method and

(b) on the basis of manufacturing technology employed to develop printers.

The quality of a printer depends on following factors such as color, Resolution, speed, memory etc. The printers are divided into impact and non-impact printer

Impact Printers

An impact printer has mechanisms resembling those of a typewriter. It forms the character or images by striking a mechanism such as a print hammer or wheel against an inked ribbon, leaving an image on paper. Impact printers are dying out however, you may come in contact with a dot-matrix printer. Examples are daisy wheel printers, dot matrix printers etc

Non-impact Printer

Non-impact printers, used almost everywhere now, are faster and quieter than impact printers because they have fewer moving parts. Non impact printers form characters and images without direct physical contact between the printing mechanism and the paper. Non impact printers often used with microcomputers are laser printers and inkjet printers etc.

Difference between Impact and Non-impact Printer

Impact Printer	Non-Impact Printer
1. Impact printers use an electromechanical mechanism that causes hammers or pins to strike against a ribbon and paper to print the text.	1. Non-impact printers do not use electromechanical printing rather it uses thermal,chemical,electrostatic, laser beam or inkjet technology for printing the text and images.
2. The efficiency of the impact printer is less as compared to non-impact printers because it uses electrical energy (external force) which is further converted into heat and sound.	2. It has higher efficiency because electrical energy is not wasted.
3. It is slow while printing.	3. It is fast while printing.
4. It uses force for printing and produces more sound while printing.	4. It does not use force and hence produces less sound while printing.
5. It cannot print graphics perfectly.	5. It can print graphics perfectly.
6. It can produce multiple copies at the same time using carbon copy.	6. It can not print multiple copies at the same time. Each paper has to be printed out separately.
7. It is usually single colored.	7. It can be single or multi colored.
8. It uses ink ribbon for printing.	8. It uses liquid or powder ink for printing.
9.It is rarely used at present.	9. It is popularly used at present.
10. Example: Dot Matrix Printer, Daisy Wheel Printer etc.	10. Example: Inkjet Printer, Laser Printer etc.

Dot-matrix Printer

Dot-matrix printer is an impact printer that produces text and graphics when tiny wire pins on the print head strike the ink ribbon. The print head runs back and forth on the paper like a typewriter. When the ink ribbon presses on the paper, it creates dots that form the text and images. Higher number of pins means that the printer prints more dots per character, thus resulting in higher print quality.

Dot-matrix printers were very popular and the most common type of printer for personal computers during the 70's and 80's. However, their use was gradually replaced by inkjet printers in the 90's. As of today, dot matrix printers are only used in some point-of-sales terminals, or businesses where the printing of carbon copy multi-part forms or data logging are needed.

Advantages of Dot Matrix Printer

Can print on multi-part forms or carbon copies.
Low printing cost per page
Reliable, durable

Disadvantages of Dot Matrix Printer

Noisy
Limited print quality
Low printing speed
Limited color printing

Inkjet Printers

Inkjet printers are non-impact printers which print text and images by spraying tiny droplets of liquid ink onto the paper. They are the most popular printers for home use. Currently, most inkjet printers use either thermal inkjet or piezoelectric inkjet technology. Thermal inkjet printer uses a heating element to heat liquid ink to form a vapor bubble, which forces the ink droplets onto the paper through the nozzle. Most inkjet manufacturers use this technology in consumer inkjet printers.

Advantages of Inkjet Printers

They are of low cost.
They are of high quality of output, capable of printing fine and smooth details.
They are capable of printing in color, good for printing pictures.
They are easy to use.
They are fast.
They are quieter than dot matrix printers.
They need no warm up time.

Disadvantages of Inkjet Printers

Print head is less durable.
Expensive replacement ink cartridges
Not good for high volume printing
Printing speed is not as fast as laser printers,
Cannot use highlighter marker on inkjet printouts

Laser Printers

Laser printers are non-impact printers which can print text and images in high speed and high quality resolution, ranging from 600 to 1200 dpi.

Unlike inkjet printers, laser printers use toner (black or colored powder) instead of liquid inks. A laser printer consists of these major components: drum cartridge, rotating mirror, toner cartridge and roller. The drum cartridge rotates as the paper is fed through. The Laser Printer mirror deflects laser beams across the surface of the drum. Laser beam creates charges and causes the toner to stick to the drum. As the drum rotates and presses on paper, toner is transferred from the drum to paper, creating images. Rollers then use heat and pressure to fuse toner to the paper. Color laser printers add colored toner in three additional passes.

Advantages of Laser Printers

They are of high resolution.
They have high print speed.
They do not smear.
They cost low per page (compared to inkjet printers).
They are good for high volume printing.

Disadvantages of Laser Printers

They are more expensive than inkjet printers.
Except for high end machines, laser printers are less capable of printing vivid colors and high quality images such as photos.
The cost of toner replacement and drum replacement is high.
Warm up time is needed

Thermal Printers

Thermal printers use two types of printing technologies: direct thermal and thermal transfer printing. Traditional thermal printers use direct thermal methods by pushing electrically heated pins against heat-sensitive paper (thermal paper). The coating on the thermal paper turns black in the areas where it is heated, producing characters or images. Direct thermal printers have no ink, toner or ribbon. These printers are durable, easy to use and cost less to print than other printers. However, they are sensitive to heat, light, water, and abrasion and the text and images may fade over time.

Plotter

Plotters are output devices used to produce single or multiple colored images and drawings. They use ink pens or ink-jet for drawing. Pens of varying colors and widths are used for shadings and line styles. The mostly used pens are wet-ink, ballpoint and felt-tip types.

Speaker

It produces and amplifies sound output. A good pair of speakers connected to a sound card will give you lots of listening pleasure. The audio output of the computer system is relayed through the speakers. More advanced speaker systems exist, allowing certain programs (such as music creation software and games) to use surround sound capabilities to beneficial effect.

Modem

Modem is a communicating device. Modem has two parts (a) Modulator and (b) Demodulator. Modulator converts digital signal into analog and demodulator converts analog signal into digital signal. Modem is a signal converter. It converts input signal into digital and output signal into analog. There are two types of modem in use: internal and external modem.

5.9 Hardware Interfaces

Peripherals are devices that are attached to a computer system to enhance its capabilities Peripherals include input devices, output devices, storage devices and communication devices. All peripherals must have some way to access the data bus of the computer (the communications channel on the motherboard that connects the processor, RAM and other components). To do this, peripherals are connected via some kind of port (also called an I/O port that is input/output) on the computer (and a cable with the proper connectors is needed).

Serial Port

Serial port is a serial communication physical interface through which information transfers in or out one bit at a time. Throughout most of the history of personal computers, the data transfer through serial ports connected with the computer to devices such as terminals and various peripherals. Serial ports are still used in these areas as they are simple, cheap and their console functions are highly standardized and widespread. A serial port requires very little supporting software from the host system. Generally, it consists of 9 pins.

Parallel Port

A parallel port is a type of interface found on the computers for connecting various peripherals. Parallel port is a parallel communication physical interface time; the parallel interface was adapted to access a number of peripheral devices other than printers. Probably one of the earliest devices to use parallel were modems, sound cards, webcams, gamepads, joysticks and external hard disk drives and CD-ROM drives. Generally, it consists of 25 pins.

USB Port

USB (Universal Serial Bus) is a newer type of serial connection that is much faster than the old serial ports. The USB is also much smarter and more versatile since it allows the “daisy chaining” of up to 127 USB peripherals connected to one port. The USB ports can support the connection of many kinds of devices (keyboard, mouse, printer, audio in/out, external floppy or Zip drives, sanner, flash drive, etc.). Newer PCs and Macs include several USB ports, some often located in handy spots on the front panel of the computer case or the side of the keyboard.

HDMI

HDMI is a High Definition Multimedia Interface. The HDMI standard was developed by multiple companies, including Hitachi, Philips, Sony, and Toshiba. It is a trademark and brand name for a digital interface used to transmit audio and video data in a single cable. It is a connector and cable capable of transmitting high-quality and high-bandwidth streams of audio and video between devices. It is supported by modern audio/video equipment, such as 4K televisions, HDTVs, audio receivers, DVD and Blu-ray players, cable boxes, and video game consoles, video and PC monitors, video projectors, home theatre receivers home-theatre-in-a-box systems, and sound bars, media streamers and network media players, smart phones (in combination with MHL), digital cameras and camcorders desktop and laptop PC.

The HDMI ports are found either on the video card or motherboard on the back of the computer. It is important to note that not all computers and video cards have HDMI connectors; your computer may use Display Port, DVI, or VGA technology.

The HDMI cables are often more expensive than analog cables since they cost more to manufacture. But, it is important to remember that a single HDMI cable can replace multiple analog cables. While other types of A/V connections require separate cables for audio and video data, a single HDMI cable carries the audio and video streams together, thereby eliminating cable clutter. For example, an analog component cable connection requires three cables for video and two for audio, totaling five cables in all. The same information can be transmitted digitally using one HDMI cable.

The HDMI eliminates the digital-to-analog and analog-to-digital conversion other interfaces require. Therefore, the HDMI typically produces the best quality picture and sound compared to other types of connections.

It also supports digital commands, allowing devices to communicate with each other. For example, if your TV is connected via HDMI to a receiver, the TV can automatically turn the receiver on and off when the TV is turned on and off.

Slots

It is referred to as an expansion port, an expansion slot, is a slot located inside a computer on the motherboard or riser board that allows additional boards to be connected to it. For example, if you wanted to install a new video card in the computer you'd purchase a video expansion card and install that card into the compatible expansion slot.

SCSI: SCSI refers to Small Computer System Interface. It is a set of American National Standards Institute (ANSI) standard electronic interfaces that allows personal computers to communicate with peripheral hardware such as disk drives, tape drives, CD-ROM drives, printers, and scanners faster data transmission rates (up to 80 megabytes per second) than standard serial and parallel ports. In addition, we can attach many devices to a single SCSI port, so that SCSI is really an I/O bus rather than simply an interface.
IDE: IDE refers to Integrated Drive Electronics. An IDE interface is an interface for mass storage devices, in which the controller is integrated into the disk or CD-ROM drive. IDE is more commonly known as advanced technology attachment (ATA) or Parallel ATA (PATA) and is a standard interface for IBM compatible hard drives. IDE is different from the Small Computer Systems Interface (SCSI) and Enhanced Small Device Interface (ESDI) because its controllers are on each drive, meaning the drive can connect directly to the motherboard Serial ATA (SATA). It is most commonly used in nearly all computers today, due to increased data transfer rate, easy cable management and cable length, increased airflow and support for more drive,
PCI: PCI refers to Peripheral Component Interconnect, a local bus standard developed by Intel Corporation A communications interface technology developed by Intel that directly connects the memory controller hub (the chip that controls the memory) to the I/O controller hub (the network interface) to eliminate network traffic through the PCI bus. The PCI architecture was designed with three main goals: to get better performance when transferring data between the computer and its peripherals, to be as platform independent as possible, and to simplify adding and removing peripherals to the system.

(XI) Ch-1 Computer System

1.1.1 Definition , characteristics and applications of computer

Advantages of Computer

Disadvantages of Computer

A) Mechanical Calculation Era:

B) Electro- Mechanical Era

C) Electronic Computer Era:

First Generation Computer(1940-1956)

2) Second Generation Computer(1956-1963)

3) Third Generation Computer(1964-Early1970's)

4) Fourth Generation Computer(Early 1970's-Till date)

Characteristics of a Fourth Generation Computer

5) Fifth Generation Computer

Bonus

On the basis of Size

Technical and Other Limitations (Disadvantages) of Mobile Computing

1.2.2 Components of Computer System (8 marks)

The major hardware components of a computer system are:

Some of the primary components of a CPU or microprocessor are given below:

Functions of the Control Unit

Arithmetic Logic Unit (ALU)

Functions of Microprocessor

Characteristics of Microprocessor

Components of Microprocessor

Types of Microprocessor

Functions of Bus Architecture:

Random Access Memory (RAM)

Types of RAM

Differences between SRAM and DRAM

Read Only Memory (ROM)

Types of ROM

Difference between RAM and ROM (Important Question)

Features of Cache Memory

L1 and L2 Cache

Buffer

1.2.6 Secondary Memory

Differences between Primary Memory and Secondary Memory[2076 Set C]

Magnetic Disk

Hard Disk

Advantages of Hard disk

Floppy Disk

Advantages of Magnetic Tape

Disadvantages of Magnetic Tape

Optical Disk

Memo Stick (Memory Stick)

Keyboard

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Technical and Other Limitations
(Disadvantages) of Mobile Computing