[15.17] How can I tell {if a key, which key} was pressed before the user presses the ENTER key?
This is not a standard C++ feature — C++ doesn't even require your system to
have a keyboard!. 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.
(By the way, the process on UNIX typically has two steps: first
set the terminal to
single-character mode, then use either select() or
poll() to test if a key was pressed. You might be able to adapt
this code.)