School SEE Computer Science

File Handling in QBASIC

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Dec 12, 2025

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The concept of a file pointer is central to understanding how data is accessed and manipulated in file handling. When a file is opened, the operating system creates a file pointer that indicates the current position within the file. This pointer moves automatically as data is read from or written to the file, and it can also be moved manually using specific functions. Understanding file pointer movement helps students work efficiently with large files, perform random access operations, and manage data storage more effectively. A file pointer always begins at a fixed position depending on the mode in which the file is opened. For example, in read mode it starts at the beginning, while in append mode it begins at the end. Functions such as fseek(), ftell(), and rewind() allow precise control over where the next read or write operation will occur. These operations are essential for tasks like modifying specific parts of a file, skipping unwanted data, or returning to the beginning for multiple scans. Mastering file pointer movement prepares students to work confidently with real-world file systems, where data access patterns are rarely linear. By understanding how the pointer shifts and how to control it, students gain a deeper insight into how computers store, retrieve, and manipulate data behind the scenes.

1. Introduction

A file is a collection of related data, information or instructions stored on a secondary storage device (like a hard disk or USB) under a unique file name.

In QBASIC, two main types of files exist:

Program File
A file that contains QBASIC instructions (source code) used for data processing.

Data File
A file that stores raw information such as name, address, marks, roll number, etc.

Example of a data file record:

File handling helps us to:

Create a data file
Store (write) data into a file
Read data from a file

QBASIC supports two types of file access:

Sequential Access (one record after another)

Random Access (jump to any record directly)

In this lesson, we focus on Sequential File Handling.

2. Basic File Operations

A QBASIC program works with files using three main steps:

OPEN a file
READ / WRITE data
CLOSE the file

3. Opening a File

Before reading or writing, you must open the file.

Syntax

Modes

ModeMeaningPurposeOUTPUTWrite onlyCreates a new file and writes from beginningINPUTRead onlyReads existing dataAPPENDAdd dataAdds new records at the end of an existing file

What happens when the file exists or does not exist?

ModeIf file existsIf file doesn't existOUTPUTOverwrites old fileCreates a new fileINPUTOpens fileError: File not foundAPPENDOpens fileCreates a new file

Examples

Alternative Syntax

4. Writing Data into a File

Steps to store data:

Open file in OUTPUT (new file) or APPEND (add to existing file)
Take inputs from user
Store data using WRITE # or PRINT #
Repeat if needed
Close the file

WRITE # Statement

Adds commas between fields and puts quotes around strings.

Example

PRINT # Statement

Adds spaces between fields, no quotes around strings.

Syntax

5. Closing a File

A file must be closed after reading or writing.

Syntax

6. Reading Data From a File

Steps:

Open file in INPUT mode
Read each record using INPUT # or LINE INPUT #
Display data
Close file

INPUT # Statement

Syntax

Example

The number and types of variables must match the data stored.

LINE INPUT # Statement

Reads an entire line as one string.

Syntax

Reading All Records: The EOF Function

EOF(file number) checks if the end of file is reached.

Used like:

7. File Management Commands

These commands work outside programs (often in Immediate Window).

CommandPurposeFILESShows list of filesCHDIRChange directoryMKDIRCreate directoryRMDIRRemove empty directoryNAME…ASRename file or folderKILLDelete a fileSHELLExecute DOS commandsSYSTEMExit QBASIC

8. Programs for Practice

You already gave dozens, so here is a summary of what types you should know:

Store single record
Store multiple records
Append records
Read all records
Read fixed number of records
Use LINE INPUT to read entire lines
Copy data from one file to another
Update records using temporary files

9. Updating Data Files in QBASIC

QBASIC cannot edit records directly.
Steps to update:
Open existing file in INPUT
Open a temporary file in OUTPUT
Read each record
Modify the record
Write modified record to temp file
Close files
Delete original file using KILL
Rename temp file using NAME … AS

10. Summary (Exam Friendly)

File Handling lets us read/write data stored on disk.
Files are opened using: OUTPUT, INPUT, APPEND.
Use WRITE # or PRINT # to store data.
Use INPUT # or LINE INPUT # to read data.
Use EOF to detect end of file.
Always close files using CLOSE.
File management commands include: FILES, MKDIR, CHDIR, RMDIR, NAME AS, KILL, SHELL, SYSTEM.