C++ FAQ Celebrating Twenty-One Years of the C++ FAQ!!!
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Section 15:
[15.18] How can I make it so keys pressed by users are not echoed on the screen?

This is not a standard C++ feature — C++ doesn't even require your system to have a keyboard or a screen. That means every operating system and vendor does it somewhat differently.

Please read the documentation that came with your compiler for details on your particular installation.