Program file
A program file has a
set of instructions and codes which are needed for data processing. It has .BAS
as an extension.
Data file
A data file has
collection of related data stored in a secondary storage device of computer.
Such a collection of data in a row is known as a record. A record in a data
file contains the detailed information of a person or anything. For example, a
record of a data file related to ‘employee’ consists of employee name, post,
department, date of birth and salary. A field is a particular data of a record.
Types of data file
1. Sequential Access
File
Sequential access file,
data is stored in sequential order. The data of a sequential access file can
only be accessed sequentially. For example, if a sequential access data file
has stored name of a person, address and age of some people then data of this
file need to access in the same order as the data are stored in a row. Since
the accessing of data from the sequential data file is done in sequential
order, the accessing data takes long time if the data file contains large
records.
2. Random access data
file
A random access file
allows us to write or read data from any location of the file. We can read or
write any record directly in a random file without searching through all the
records that precede it. Thus, reading and writing of data is faster than
sequential access data file.
How to open a
sequential data file?
OPEN statement is used
to open a sequential data file.
Syntax 1: OPEN FOR AS #
Filenumber
Where,
Filename is the name of
the sequential data file.
Mode determines the
operation of data file like OUTPUT, INPUT and APPEND. The different modes and
their purposes are listed below.
OUTPUT mode
To create a new
sequential data file and store data in it.
INPUT mode
To retrieve the
contents of the existing data file.
APPEND mode
To add more records in
the existing data file.
File number is a number
from 1 to 255 that identifies the data file.
REM to create a new
sequential data file and to store data.
CLS
OPEN “employee.dat” FOR
OUTPUT AS # 1
DO
INPUT “Enter employee name “;n$
INPUT “Enter address”; a$
INPUT “Enter post”;p$
INPUT “Enter salary”; sal
WRITE#1, n$,a$,p$,sal
INPUT “Do you need more records (y/n)”;
ch$
LOOP WHILE UCASE$(ch$)
= “Y”
CLOSE#1
END
REM to display the
content of datafile
CLS
OPEN “employee.dat” FOR
INPUT AS # 1
PRINT “Name”,
“Address”, “Post”, “Salary”
WHILE NOT EOF (1)
INPUT#1, n$,a$,p$,sal
PRINT n$,a$,p$,sal
WEND
CLOSE#1
END
REM add more records to
the data file
CLS
OPEN “employee.dat” FOR
APPEND AS # 1
DO
INPUT “Enter employee name “;n$
INPUT “Enter address”; a$
INPUT “Enter post”;p$
INPUT “Enter salary”; sal
WRITE#1, n$,a$,p$,sal
INPUT “Do you need more records (y/n)”;
ch$
LOOP WHILE UCASE$(ch$)
= “Y”
CLOSE#1
END
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