written in a computer language.
(b) The files of computer are classified into program file and data file.
(c) QBASIC supports two types of data file. They are
(a) A data file is a collection of programs. FALSE
(b) A program can be used to create a data file. TRUE
(c) Only one program can use a data file. FALSE
(d) A data file can be created,modified or deleted. TRUE
(e) In a sequential access data file, data can be read from any position. FALSE
(f) Data can be added or appended in a sequential data file. TRUE
(g) Data can be copied from one data file to another. TRUE
(h) Output mode is used to create new data file. TRUE
AS #File_number
Purpose: OPEN statements opens a sequential for only one purpose : either reading or writing.
(b) CLOSE
Syntax: CLOSE [#File_number,] [#File_number] Where, #File_number of an open file.
Purpose: CLOSE statement is used to close the data file.
(c) WRITE #
Syntax: WRITE [#File_number,] Expression List
Purpose: WRITE statement sends one or more data items to the specified file.
(d) INPUT #
Syntax: INPUT #File_number, Variable List
Where,
#File_number The number of an open file.
Variable List One or more variables separated by a comma.
Purpose: INPUT# statement is used to extract the data items from a data file for reading purpose.
(e) INPUT$( )
Syntax: INPUT$ ( n , [#file_number])
Where,
n The number of characters (bytes) to read.
#file_number The number of an open file.
Purpose: INPUT$( ) reads the specified number of character from the data file.
(f) EOF ( )
Syntax: EOF(#File_number)
Where,
#File_number Number of the open file that is needed to be read.
Purpose: EOF( ) is used to detect the End of the file.
(g) KILL
Syntax: KILL “filename”
Purpose: KILL statement is used to delete the file or files.
(h) NAME
Syntax: NAME “oldname” AS “Newname”
Purpose: NAME statement is used to rename the data file.
(i) FILES
Syntax: FILES [Filespace$]
Where, Filespace$ may include filenames or path.
Purpose: The FILE statement displays the files of the current subdirectory or specified subdirectory.
(j) MKDIR
Syntax: MKDIR Path,
Where, Path is the sequence of directory and subdirectories.
Purpose: MKDIR is used to creates a subdirectory which is used to manage them.
(k) CHDIR
Syntax: CHDIR
Purpose: The CHDIR statement allows QBASIC to change from one directory to another.
(l) RMDIR
Syntax: RMDIR Path
Where, Path is the sequence of directory and subdirectories.
Purpose: RMDIR statement is used to remove or delete only subdirectory from a disk.
(m) SHELL
Syntax: SHELL [DOS command]
Purpose: This command allows to exit from QBASIC to DOS prompt temporarily or to execute DOS commadns from QBASIC.
(n) LINE INPUT#
Syntax: LINE INPUT [#file number] ["prompt";] variable$
Purpose : The LINE INPUT statement reads the entire line or maximum 255 characters from the keyboard or from the sequential file up to a carriage return.
4. Write algorithms for the following statements:
(a) To read name,address and salary of 10 different persons from the keyboard and store them in a data file.
Algorithm:
Step 1: Open the data file to read the data (Input mode)
Step 2: Set I = 1
Step 3: Read the data from the data file (Name, Address and Salary)
Step 4: Display the data on the screen
Step 5: Increment I by 1 i.e. I=I+1
Step 6: Check the I. Is I<=10.
If Yes: Repeat Step 3,4,5,6
If No: Go to step 7.
Step 7: Close the data file
Step 8: Stop
(b) To read all data (Name, Address and Salary ) from the data file and display them on the screen.
Algorithm:
Step 1: Open the data file to read the data (Input mode)
Step 2: Read the data from the data file (Name, Address and Salary)
Step 3: Display the data on the screen
Step 4: Close the data file
Step 5: Stop
5. Answer the following questions:
a. Define a file. Differentiate between a data file and a program file.
ANSWER: A Collection of data or information or instructions which are stored permanently in the secondary storage device using a unique filename is called file.
| Data File |
Program File |
|---|
| 1. A collection of the related data stored in the hard disk or any other secondary storage devices separately from the program that uses it. |
1. A file which contains instructions, which are used to manipulate data and give the output and stored in the secondary storage devices is called program file. |
b. What are sequential access data file and random access data file?
ANSWER:
Sequential Access Data File:
A sequential data file conducts reading and writing operation sequentially, from the beginning of the file to the end. For example, if you store 10 different data and if you want read , 9th data, then you will have to pass through the 1st to 8th data to search the 9th data; there is no way to directly go to it.
Random Access Data File:
A random data file conducts reading and writing operations randomly. It is suitable for the database that requires direct access to individual records stored on the disk. For example, to read 100th data item, one does not need to go through all the data from 1 to 99. Data number 100 can be directly accessed without going through other data items.
c. What are the advantages of creating a data file?
ANSWER:
The advantages of creating data file are as follows:
Once a data file is created , it can be reused.
Different programs can share the same data file.
It can be created, modified or deleted.
A data file can store a large output for the future use.
d. What are the three different operations of a data file? Explain them.
ANSWER:
The three modes of operations of data file are as follows:
| Mode of File |
Function |
|---|
| Output Mode | For writing data or information to a new file |
| Input Mode |
For reading data or information from a data file |
| Append Mode |
Appending information or data to the end of an existing file |
e. Differentiate between INPUT # and LINE INPUT # statement.
ANSWER:
INPUT #
Syntax: INPUT #File_number, Variable List
Where,
#File_number The number of an open file.
Variable List One or more variables separated by a comma.
Purpose: INPUT# statement is used to extract the data items from a data file for reading purpose.
LINE INPUT #
Syntax: LINE INPUT [#file number] [“Prompt”] ;Variable$
Where,
Prompt It is an optional string of characters enclosed in quotes to prompt for input.
Variable$ String variable to which LINE INPUT assigns all characters.
Purpose: LINE INPUT is used to store data only is the string variable and can reads the entire line or maximum 255 characters from the keyboard or from the sequential file up to a carriage return.
f. What is the use of the “file number” of the data file? Write the range of the file number.
ANSWER: The file number is used in a data file to identify the each file with a unique number . When a file is open, its unique file number identifies it.
File number may be integer number from 1 to 255.
g. Differentiate between input mode and output mode.
ANSWER:
| Input Mode | Output Mode |
| 1. Open a file in reading mode. | 1. Open a new file to write data. |
| 2. It never creates a new data file. |
2. It always creates a new data file. |
| 3. Old records will not be deleted in this mode. |
3. Old records will be deleted in this mode. |
h. Differentiate between output mode and append mode.
ANSWER:
| Output Mode | Append Mode |
|---|
| 1. It always creates a new data file. | 1. If the specified file does not exist , APPEND creates it. |
| 2. Old records will be deleted in this mode. | 2. Old records will not be deleted in this mode. |
6. Debug the following programs and test them in the computer.
a. REM to add or append data
OPEN “C:\SAL,DAT”FOR OUTPUT AS #1
DO
CLS
INPUT”ENTER THE NAME::::::::”;N$
INPUT”ENTER THE POST::::::::::”;P$
INPUT”ENTER SALARY”;S
WRITE # 2, N$, P$, S
INPUT ”Want To Supply More Y/N::”;CH
LOOP WHILE UCASE$(CH) = ”Y”
CLOSE #2
END
b. REM to copy data from”SAL.DAT” to “TEMP.DAT”
OPEN “SAL.DAT” FOR INPUT AS # 1
OPEN”TEMP.DAT” FOR OUTPUT AS #2
CLS
DO
INPUT #2, N$, P$, S
WRITE #2, N$, P$, S
LOOP WHILE NOT EOF( )
CLOSE #2, #1
END
7. Type the following programs and see the outputs.
a. REM to create data file
DECLARE SUB ADDREC( )
CALL ADDREC
END
SUB ADDREC
CLS
OPEN”STAFF.DAT” FPR OUTPUT AS #1
DO
INPUT ”Enter Name:”;N$
INPUT” Enter address;”;A$
INPUT “Enter Salary”;S
WRITE #1, N$, A$, S
INPUT”Wants to Continue Y/N”;C$
C$= UCASE$(C$)
LOOP WHILE C$=”Y”
CLOSE #1
END SUB
b. REM to read and display the data
DECLARE SUB DISPREC ( )
CALL DISPREC
END
SUB DISPREC
CLS
PRINT ”NAME”,”ADDRESS”,”SALARY”
OPEN “STAFD.DAT” FOR INPUT AS #1
DO
INPUT #1, N$, AD$, SAL
PRINT N$, AD$, SAL
LOOP WHILE NOT EOF (1)
CLOSE #1
END SUB
c. REM to display selected data
DECLARE SUB DISPREC ( )
CALL DISPREC
END
SUB DISPREC
CLS
PRINT ”NAME”,”ADDRESS”,”SALARY”
OPEN “STAFF.DAT” FPR INPUT AS #1
DO
INPUT #1, N$, AD$, SAL
IF SAL>= 35000 THEN
PRINT N$, AD$, SAL
END IF
LOOP WHILE NOT EOF ( )
CLOSE #1
END SUB
d. REM to copy data from one data file to another.
DECLARE SUB DATACOPY ( )
CALL DATACOPY
END
SUB DATACOPY
CLS
OPEN”SATFF.DAT” FOR INPUT AS #1
OPEN”TEMPT.DAT” FOR OUTPUT AS #2
DO
INPUT#1, N$, AD$, SAL
IF UCASE$(AD$) = “KATHMANDU” THEN
WRITE #2, N$, AD$, SAL
END IF
LOOP WHILE NOT EOF ( )
CLOSE #1, #2
END SUB
e. REM to count records of data file
DECLARE SUB DISPREC ( )
CALL DISPREC
END
SUB DISPREC
CLS
OPEN “STAFF.DAT” FOR INPUT AS #1
C=1
DO
LINE INPUT #1, N$
C=C+1
LOOP WHILE NOT EOF (1)
CLOSE #1
PRINT ”Total Records=”;C
END SUB
8. Write the programs for the following:
To create a data file that stores name, address and salary for at least ten different persons.
ANSWER:
OPEN "EMPLOYEE.TXT" FOR OUTPUT AS #1
FOR P = 1 TO 10
INPUT "ENTER NAME,ADDRESS AND SALARY", NAME$, ADDRESS$, SALARY
WRITE #1, NAME$, ADDRESS$, SALARY
NEXT P
CLOSE #1
END
Write a program to store name, roll no and marks for three subjects in a sequential data file named “STUDENT.DAT”. The program should terminate according to the user’s choice.
ANSWER:
OPEN "STUDENT.DAT" FOR OUTPUT AS #1
DO
INPUT “Enter name,roll and marks in 3 subjects ” , NAME$, ROLL, SUB1, SUB2, SUB3
WRITE #1, NAME$, ROLL, SUB1, SUB2, SUB3
INPUT “DO YOU WANT TO ADD SOME MORE RECORDS (Y/N) ” , CH$
LOOP WHILE UCASE$(CH$) = “Y”
CLOSE #1
END
Write a program to input data from the data file named “student.dat” which, contains name, roll no and marks for three subjects for n number of students. Calculate total and percentage and display the result on the screen.
ANSWER:
CLS
OPEN "STUDENT.DAT" FOR INPUT AS #1
PRINT "NAME", "ROLL", "SUB1", "SUB2", "SUB3", "TOTAL", "PERCENTAGE”
WHILE NOT EOF(1)
INPUT #1, NAME$, ROLL, SUB1, SUB2, SUB3
TOTAL = SUB1 + SUB2 + SUB3
PERCENTAGE = TOTAL / 3
PRINT NAME$, ROLL, SUB1, SUB2, SUB3, TOTAL, PERCENTAGE
WEND
CLOSE #1
END
Write a program to open a data file named “STUDENT.DAT” and add some data on it. Fields of the data file are “Name”, “Address”, “Telephone”.
ANSWER:
OPEN “STUDENT.DAT” FOR APPEND AS #1
DO
INPUT “Enter name,address and telephone ”; NAME$, ADDRESS$, TELEPHONE$
WRITE #1, NAME$, ADDRESS$, TELEPHONE$
INPUT “DO YOU WANT TO ADD SOME MORE RECORDS”; CH$
LOOP WHILE UCASE$(CH$) = “Y”
CLOSE #1
END
Write a program to ask item name, sold quantity, amount and salesman’s name and store them in a sequential data file “SALES.DAT”. Ask the user if he/she wants to enter another data or not.
ANSWER:
OPEN “SALES.DAT” FOR OUTPUT AS #1
DO
INPUT “Enter item name, sold quantity , amount , salesman’s name ” ; ITEMNAME$, SOLDQTY , AMOUNT ,SALES NAME$
WRITE #1, ITEMNAME$ , SOLDQTY , AMOUNT , SALES NAME$
INPUT “ DO YOU WANT TO ADD SOME MORE RECORDS ” ; CH$
LOOP WHILE UCASE$(CH$) = “Y”
CLOSE #1
END
Write a program to read all the data of the data file named “SALES.DAT”, where fields are unknown. Display the result on the screen.
ANSWER:
OPEN “SALES.DAT” FOR INPUT AS #1
WHILE NOT EOF(1)
INPUT #1, ITEMNAME$ , SOLDQTY , AMOUNT , SALES NAME$
PRINT ITEMNAME$ , SOLDQTY , AMOUNT , SALES NAME$
WEND
CLOSE #1
END
A data file named “STUDENT.DAT” contains a number of records. Write a program to display all records from records number 5 to 10.
ANSWER:
OPEN "STUDENT.TXT" FOR INPUT AS #1
WHILE NOT EOF(1)
INPUT #1, SN, NAME$
IF SN >= 5 AND SN <= 10 THEN
PRINT SN, NAME$
END IF
WEND
CLOSE #1
END
Write a program to read all the data from the data file “SALES.DAT” and copy them to another data file named “TEMP.DAT”.
ANSWER:
OPEN "SALES.DAT" FOR INPUT AS #1
OPEN "TEMP.DAT" FOR OUTPUT AS #2
WHILE NOT EOF(1)
INPUT #1, ITEMNAME$, SOLDQTY, AMOUNT, SALESMANNAME$
WRITE #2, ITEMNAME$, SOLDQTY, AMOUNT, SALESMANNAME$
WEND
CLOSE #1, #2
END
A data file contains names, marks of three subjects and total marks. Write a program to read the name from the keyboard and display information on the monitor. If the required data is located inside the data file, otherwise display, a message “DATA NOT FOUND”.
ANSWER:
OPEN “MARKS.DAT” FOR INPUT AS #1
INPUT “ ENTER THE NAME FOR SEARCH ”, NS$
FLAG = 0
DO
INPUT #1, NAME$ , SUB1 , SUB2 , SUB3
IF NAME$ = SN$ THEN
PRINT NAME$ , SUB1 , SUB2 , SUB3
FLAG=1
EXIT DO
END IF
LOOP WHILE NOT EOF(1)
IF FLAG=0 THEN PRINT “DATA NOT FOUND”
CLOSE #1
END
A data file contains the names of students , marks of three subjects and total marks of n number of students. Write a program to display the data for only those students whose total marks is greater than 100 but less than 150.
ANSWER:
OPEN “MARKS.DAT” FOR INPUT AS #1
WHILE NOT EOF(1)
INPUT #1, NAME$ , SUB1 , SUB2 , SUB3 , TOTAL
IF TOTAL > 100 AND TOTAL < 150 THEN
PRINT NAME$ , SUB1 , SUB2 , SUB3 , TOTAL
END IF
WEND
CLOSE #1
END
Write a program to input the name of a student to delete his/her data from the data file named “STUDENT.DAT”. The data file contains name, roll no and marks for three different subjects.
ANSWER:
OPEN “MARKS.DAT” FOR INPUT AS #1
OPEN “TEMP.DAT” FOR OUTPUT AS#2
INPUT “ ENTER THE NAME TO BE DELETED ”, D$
DO
INPUT #1,N$,R,S1,S2,S3
IF N$<>D$THEN
WRITE #2,N$,R,S1,S2,S3
ELSE
PRINT “DELETED DATA”;N$,R,S1,S2,S3
END IF
LOOP WHILE NOT EOF(1)
CLOSE #1,#2
KILL “MARKS.DAT”
NAME “TEMP.DAT” AS “MARKS.DAT”
END
A data file named “STUDENT.DAT” contains some records. Write a program to content total records of the data file.
ANSWER:
OPEN “ STUDENT.DAT” FOR INPUT AS #1
C = 0
DO
LINE INPUT #1, N$
C = C + 1
LOOP WHILE NOT EOF(1)
CLOSE #1
PRINT “TOTAL RECORDS” ; C
END
A data file named “STUDENT.DAT” contains some records having fields name and marks in three subjects. Write a program to display all the records on the monitor if the marks in each subject are > = 60.
ANSWER:
OPEN “STUDENT.DAT” FOR INPUT AS #1
WHILE NOT EOF(1)
INPUT #1, NAME$ , SUB1 , SUB2 , SUB3
IF SUB1 >= 60 AND SUB2 >= 60 AND SUB3 >= 60 THEN
PRINT NAME$ , SUB1 , SUB2 , SUB3
END IF
WEND
CLOSE #1
END
A data file named “OFFICE.DAT” contains some records having fields name, post and salary. Write a program to count the total number of officers in the office.
ANSWER:
OPEN “STUDENT.DAT” FOR INPUT AS #1
WHILE NOT EOF(1)
INPUT #1, NAME$ , POST$, SALARY
IF POST$ = “OFFICER” THEN
C = C + 1
PRINT NAME$ , POST$, SALARY
END IF
WEND
CLOSE #1
END
Debug the following programs and test them in computer.
REM to add or append
OPEN “C:\SAL.DAT” FOR OUTPUT AS #1
DO
CLS
INPUT “ENTER NAME” ; N$
INPUT “ENTER POST” ; P$
INPUT “ENTER SALARY” ; S
WRITE #2, N$ , P$, S
INPUT “ WANTS TO SUPPLY MORE Y/N” ; CH
LOOP WHILE UCASE$(CH)= “Y”
CLOSE #2,#1
END
Corrected Program
REM to add or append
OPEN “C:\SAL.DAT” FOR APPEND AS #1
DO
CLS
INPUT “ENTER NAME” ; N$
INPUT “ENTER POST” ; P$
INPUT “ENTER SALARY” ; S
WRITE #1, N$ , P$, S
INPUT “ WANTS TO SUPPLY MORE Y/N” ; CH$
LOOP WHILE UCASE$(CH$)= “Y”
CLOSE #1
END
REM to copy data from “SAL.DAT” to “TEMP.DAT”
OPEN “SAL.DAT” FOR INPUT AS #1
OPEN “TEMP.DAT” FOR OUTPUT AS #2
CLS
DO
INPUT #2,N$,P$,S
WRITE # 2, N$ , P$, S
LOOP WHILE NOT EOF( )
CLOSE #2,#1
END
Corrected Program
REM to copy data from “SAL.DAT” to “TEMP.DAT”
OPEN “SAL.DAT” FOR INPUT AS #1
OPEN “TEMP.DAT” FOR OUTPUT AS #2
CLS
DO
INPUT #1 , N$ , P$ , S
WRITE # 2 , N$ , P$ , S
LOOP WHILE NOT EOF( 1 )
CLOSE #1 , #2
END
***** END OF CHAPTER - 13 *****
