Binary vs. Text File Modes: What are the Key Differences in C File Handling?

Unveiling the Mysteries: Differences in File Writing Modes

In the realm of file handling, the choice between binary and text modes is crucial. To delve into this distinction, we will consider an example in MS Visual C.

Consider an array of characters buffer and the following file pointers:

FILE *fp_binary = fopen(filename, "wb");
FILE *fp_text = fopen(filename, "wt");

Binary Mode: A Direct Transmission

In binary mode ("wb"), data written to the file is transferred verbatim. There is no conversion or translation of characters. Each byte in the buffer is written directly onto the storage medium.

Text Mode: A Subtle Transformation

In text mode ("wt"), however, a hidden translation occurs. Specifically, on the Windows platform, the following operations take place:

• Line feeds ('n') are converted to 'rn' sequences on output.
• Carriage return/line feed sequences are transformed to line feeds on input.
• In append mode, a trailing control character (ctrl-z) may be stripped from the end of the file, and its presence is interpreted as an end-of-file marker.

Practical Implications

These subtle transformations in text mode can have consequences for certain file operations. For example, newline characters may appear differently in text editors depending on the mode used to open the file. Additionally, binary files should always be opened in binary mode to avoid unexpected data corruption.

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