What is File Handling?

File Handling is the process of creating, opening, reading, writing, appending, and closing files in a program. It allows data to be stored permanently, even after the program ends.

Definition

File handling in C is the process of storing and retrieving data from files using file operations.

Why Do We Need File Handling?

Without file handling:

  • Data is stored only in RAM (temporary memory).
  • Data is lost when the program ends.

With file handling:

  • Data is stored permanently on the hard disk.
  • It can be used later.

Example:

  • Student records
  • Employee details
  • Bank transactions
  • Attendance system

Steps in File Handling

  1. Declare a file pointer.
  2. Open the file.
  3. Perform file operations (read/write/append).
  4. Close the file.

File Pointer

A file pointer is used to access a file.

Syntax

FILE *fp;
  • FILE is a predefined data type.
  • fp is the file pointer.

Opening a File

Use the fopen() function.

Syntax

fp = fopen("filename", "mode");

Example:

fp = fopen("student.txt", "w");

File Modes

ModeMeaning
"r"Read an existing file
"w"Write to a file (creates a new file or overwrites an existing file)
"a"Append data at the end of a file
"r+"Read and write
"w+"Read and write (overwrites existing content)
"a+"Read and append

Writing to a File

Use fprintf().

Example

#include <stdio.h>

int main()
{
    FILE *fp;

    fp = fopen("student.txt", "w");

    fprintf(fp, "Welcome to File Handling in C.");

    fclose(fp);

    printf("Data written successfully.");

    return 0;
}

Output

Data written successfully.

Contents of student.txt:

Welcome to File Handling in C.

Reading from a File

Use fgets().

Example

#include <stdio.h>

int main()
{
    FILE *fp;
    char text[100];

    fp = fopen("student.txt", "r");

    fgets(text, 100, fp);

    printf("%s", text);

    fclose(fp);

    return 0;
}

Output

Welcome to File Handling in C.

Appending Data

Use append mode ("a") to add data without deleting the existing content.

Example

#include <stdio.h>

int main()
{
    FILE *fp;

    fp = fopen("student.txt", "a");

    fprintf(fp, "\nThis is appended text.");

    fclose(fp);

    return 0;
}

File Contents

Welcome to File Handling in C.
This is appended text.

Closing a File

Use fclose().

Syntax

fclose(fp);

Closing a file:

  • Saves changes.
  • Frees system resources.

Checking if the File Opened Successfully

Always check if fopen() returns NULL.

Example

#include <stdio.h>

int main()
{
    FILE *fp;

    fp = fopen("student.txt", "r");

    if (fp == NULL)
    {
        printf("File cannot be opened.");
        return 1;
    }

    printf("File opened successfully.");

    fclose(fp);

    return 0;
}

Common File Functions

FunctionPurpose
fopen()Opens a file
fclose()Closes a file
fprintf()Writes formatted data to a file
fscanf()Reads formatted data from a file
fgetc()Reads one character
fputc()Writes one character
fgets()Reads one line
fputs()Writes one line

Memory Diagram

Program
   |
   |
 FILE Pointer (fp)
   |
   |
student.txt
-------------------------
Welcome to C
File Handling
-------------------------

The file pointer connects the program to the file.

Real-Life Example

Think of a Notebook.

  • Notebook → File
  • Pen → File pointer
  • Writing in the notebook → fprintf()
  • Reading from the notebook → fgets()
  • Closing the notebook → fclose()

Structure of a File Program

FILE *fp;

fp = fopen("data.txt", "w");

fprintf(fp, "Hello");

fclose(fp);

Advantages of File Handling

  • Stores data permanently.
  • Handles large amounts of data.
  • Enables data sharing between program executions.
  • Reduces memory usage.
  • Makes applications more reliable.

Exam Definition

File handling in C is the process of creating, opening, reading, writing, appending, and closing files to store data permanently using file operations.

Category: MCA

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