Working with Binary Files

Binary files store data in raw format, which allows efficient reading and writing without converting data to text.

In this lesson, you will learn:

• How to write data to a binary file using fwrite().
• How to read data from a binary file using fread().
• The difference between binary and text file handling.

Opening a Binary File

Binary files are opened using the fopen() function with a mode containing b.

Example:

FILE *filePtr = fopen("data.bin", "wb");

This opens data.bin for writing in binary mode.

Writing to a Binary File

The fwrite() function writes binary data to a file.

Syntax:

fwrite(&data, size, count, filePtr);

Example:

fwrite(&num, sizeof(int), 1, filePtr);

This writes an integer to the file.

Example: Writing to a Binary File

This program demonstrates writing an integer to a binary file.

#include <stdio.h>

int main() {
    FILE *filePtr = fopen("data.bin", "wb");
    if (filePtr == NULL) {
        printf("Error opening file!\n");
        return 1;
    }
    int num = 42;
    fwrite(&num, sizeof(int), 1, filePtr);
    fclose(filePtr);
    return 0;
}

Reading from a Binary File

The fread() function reads binary data from a file.

Syntax:

fread(&data, size, count, filePtr);

Example:

fread(&num, sizeof(int), 1, filePtr);

This reads an integer from the file.

Example: Reading from a Binary File

This program demonstrates reading an integer from a binary file.

#include <stdio.h>

int main() {
    FILE *filePtr = fopen("data.bin", "rb");
    if (filePtr == NULL) {
        printf("Error opening file!\n");
        return 1;
    }
    int num;
    fread(&num, sizeof(int), 1, filePtr);
    printf("Number read from file: %d\n", num);
    fclose(filePtr);
    return 0;
}

Appending to a Binary File

Use ab mode to append binary data to a file:

FILE *filePtr = fopen("data.bin", "ab");

This keeps existing data and adds new data at the end of the file.

Text vs Binary Files

Text files:

• Store data as human-readable characters.
• Use fprintf() and fscanf().

Binary files:

• Store data in raw format.
• Use fwrite() and fread().

Summary

In this lesson, you learned:

• How to write and read binary files using fwrite() and fread().
• The difference between text and binary file operations.
• How to append binary data to an existing file.

Next, we will explore error handling in file operations!