Text vs. Binary File Modes: What are the Key Differences and Implications?

Text Mode vs. Binary Mode: Uncovering the Discrepancies

When dealing with files, it's critical to understand the distinction between text mode and binary mode. While operating with files opened in text mode, specific translations occur that differ from those in binary mode.

Example in MS Visual C

Consider the following code snippet, where a buffer containing character values is written to two files, one opened in binary mode and the other in text mode:

unsigned char buffer[256];
for (int i = 0; i < 256; i++) buffer[i]=i;
int size  = 1;
int count = 256;

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

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

Text Mode Translation

In MS Visual C, opening a file in text mode causes specific translations to occur during writing:

• Newline characters ('n') are converted to 'rn' sequences.
• Carriage return/newline sequences are converted to line feeds.
• If the file is opened in append mode, a control-Z (Ctrl Z) character may be removed from the end of the file and interpreted as the end of file.
• A control-Z character will not be appended, as previously believed.

Implications

These translations in text mode ensure that line endings conform to Windows conventions, which can be important for compatibility with text-based applications. However, for handling binary data, using binary mode is essential to avoid any unexpected translations that could corrupt the data.

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