Text and Binary Streams in C

What is a Stream in C?

A stream is simply a flow of data. In C, all input and output operations are done through streams. You can think of it as a path through which data moves between your program and a file, keyboard, or screen.

There are two main types of streams in C:

• Text Stream
• Binary Stream

Text Streams in C

A text stream is a sequence of characters. It translates certain characters during input and output. For example:

• Newline characters (\n) in Unix or Linux get converted to \r\n in Windows.
• End-of-file (EOF) markers might be handled specially.

Key Features:

• Data is stored as human-readable characters.
• Text mode handles newline conversion depending on the system.
• Useful for editing files manually.

Opening Files in Text Mode:

Use fopen() function with one of these modes:

fopen("filename.txt", "r");  // read mode
fopen("filename.txt", "w");  // write mode
fopen("filename.txt", "a");  // append mode

Example: Writing to a Text File

#include <stdio.h>
 
int main()
{
    // Open a text file in write mode
    FILE *quiz = fopen("quiz.txt", "w");
 
    if (quiz == NULL)
   {
        perror("Failed to open file");
        return 1;
    }
 
    fputs("Welcome to Sanfoundry Certification!\n", quiz);
    fputs("Your score is 95/100\n", quiz);
 
    fclose(quiz);  // Always close the file
    return 0;
}

Binary Streams in C

A binary stream is a sequence of bytes. No translation is done — data is read and written exactly as it is.

Key Features:

• Data is stored in raw byte format.
• No newline or EOF conversion.
• Best for storing structured data (e.g., structs, images).

Opening Files in Binary Mode:

Use fopen() with b in the mode:

fopen("filename.bin", "rb");  // read in binary
fopen("filename.bin", "wb");  // write in binary
fopen("filename.bin", "ab");  // append in binary

Example – Writing to a Binary File

#include <stdio.h>
#include <stdlib.h>
 
int main()
{
    // Binary write
    FILE *certification = fopen("certification.dat", "wb");  
 
    if (certification == NULL) {
        perror("File open failed");
        return 1;
    }
 
    int scores[] = {90, 85, 88, 92};
    // Write binary data
    fwrite(scores, sizeof(int), 4, certification);  
 
    fclose(certification);
    return 0;
}

Comparison: Text vs Binary Streams

Best Practices

• Mode Selection: Always open files in the appropriate mode (“r”/”w” for text, “rb”/”wb” for binary).
• Error Checking: After opening a file, check if the file pointer is NULL to ensure the file was opened successfully.
• Resource Management: Always close files using fclose() to free system resources.
• Portability: Be cautious of platform-specific behaviors, especially regarding line endings in text files.
• Data Integrity: When dealing with binary files, ensure that the data structures are consistent across different systems to avoid issues with endianness or padding.

Sanfoundry Global Education & Learning Series – 1000 C Tutorials.