Windows File Handling: Writing Binary Files Correctly

Thu, 07 May 2026 03:33:58 +0000

You’ve just finished writing some critical data to a file – maybe configuration settings, image data, or serialized objects. You check the file, and it’s corrupted. What happened? The most likely culprit is how you told Windows to handle that data, particularly if you weren’t explicit about it being binary.

The Core Problem: Unintended Transformations

Windows, at its lowest level, treats all files as raw sequences of bytes. It doesn’t inherently know or care if you’re writing text or a compiled executable. The confusion arises from higher-level libraries, especially the C Runtime (CRT), which introduce modes that can automatically alter your data. The default behavior on Windows is often to assume text files, and this assumption can silently corrupt binary data.

File I/O on The Coders Blog

Windows File Handling: Writing Binary Files Correctly

The Core Problem: Unintended Transformations