Binary vs. Text File Writing in MS Visual C : When Should I Use Which Mode?

Binary vs. Text Mode File Writing in MS Visual C

When writing data to a file in MS Visual C, the choice between binary mode and text mode has significant implications. Binary mode provides direct access to the underlying data, while text mode performs character translation that can alter the original content.

Binary Mode

In binary mode, the data is written directly to the file without any modifications. This means that the characters are stored as their binary representations, without any additional encoding or translation. This is suitable for writing binary data such as images, videos, or executables.

FILE *fp_binary = fopen(filename, "wb");
fwrite(buffer, size, count, fp_binary);

Text Mode

In contrast, text mode converts newline characters ('n') to the Windows-specific carriage return/line feed sequence ('rn'). This compatibility with legacy operating systems is essential for text files that will be read by other programs.

FILE *fp_text = fopen(filename, "wt");
fwrite(buffer, size, count, fp_text);

Additional Considerations

When a file is opened in text mode in Windows, several additional effects occur:

• Line Feed Translation: Newline characters are translated to 'rn' upon output and translated from 'rn' to 'n' upon input.
• Carriage Return/Line Feed Translation: Carriage return/line feed sequences are interpreted as line feeds on input.
• Ctrl-Z Handling: If the file is opened in append mode, a ctrl-z character (character 26) may be interpreted as the end of the file.

Understanding these differences is crucial for writing data correctly and ensuring compatibility with other applications. Choosing the correct mode depends on the nature of the data and the intended use of the file.

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