I was just debugging a program in gdb and somehow I found a new feature I've never seen or even heard of before, a split view where I can see and browse the code in addition to giving commands:
What is this? What did I do, or, more specifically, how can I get this split-screen mode again? Is there a name for this mode, or somewhere I can read about how to use it?
It's called the TUI (no kidding). Start for example with gdbtui
or gdb -tui
...
Please also see this answer by Ciro Santilli. It wasn't available in 2012 to the best of my knowledge, but definitely worth a look.