I'm wondering how people used to write DOS games (like Doom), I can't find much on this, but would love to learn more about the earlier days of game development.

What language was used predominantly?

I presume it was C. Or C++ already?

What IDEs (or editors/compilers) were popular?

Microsoft Visual C/C++ (or Microsoft C/C++ as I believe it used to be called) didn't exist back then AFAIK. So what did people use? edit and a command-line compiler from Intel or something?

What APIs where used?

What was common for 2D games? What about 3D games like Doom and Tomb Raider?

Anything else that's different from today?

I'd be happy to hear any other differences, like what image/audio formats were used.