How can I tell {if a key, which key} was pressed before the user presses the ENTER key?, C++ FAQ

C++ FAQ

From Marshall Cline: Bjarne Stroustrup, Herb Sutter, Andrei Alexandrescu, Pearson / Addison-Wesley Publishers and I collaborated to create a new C++ Super-FAQ! It's a team effort, with huge contributions from each of us and with amazing support from dozens of brilliant editors. The result is "awesomer" than ever! I originally wrote/published the FAQ in 1991 and now look forward to this new phase - and to continue working with it for another 20 years!

On a personal note, I'm at Oculus VR and it is amazing - fabulous people doing fabulous work. We're hiring more fabulous people so write me if that's you!

FAQ: How can I tell {if a key, which key} was pressed before the user presses the ENTER key? ←(in the new Super-FAQ)

It's in Section: Input/output via <iostream> and <cstdio>:

FAQ: Advantages of <iostream> over <cstdio>?
FAQ: Understanding infinite loop when the input is invalid?
FAQ: How can I get std::cin to skip invalid input characters?
FAQ: How does that funky while (std::cin >> foo) syntax work?
FAQ: Why does my input seem to process past the end of file?
FAQ: Why is my program ignoring my input request after the first iteration?
FAQ: Should I end my output lines with std::endl or '\n'?
FAQ: How can I provide printing for my class Fred?
FAQ: Using a printOn() method vs. a friend function?
FAQ: How can I provide input for my class Fred?
FAQ: Providing printing for an entire hierarchy of classes?
FAQ: How can I open a stream in binary mode?
FAQ: "Reopening" std::cin and std::cout in binary mode?
FAQ: How can I write/read objects of my class to/from a data file?
FAQ: Sending objects over a network?
FAQ: Backslashes in filenames?
FAQ: How to capture key presses before the ENTER key? (this FAQ)
FAQ: How to turn off screen echo on keyboard input?
FAQ: How can I move the cursor around on the screen?
FAQ: How can I clear the screen?
FAQ: How can I change the colors on the screen?
FAQ: How can I print the numeric value of a char or char*?