LPC
The C-flavoured, object-oriented language LPMud worlds were written in — and the one thousands of teenagers learned to program on.
Lars Pensjö at Chalmers designed LPC in 1989 as LPMud's built-in language. The syntax came from C, the model did not: every file was an object, inheritance meant inherit-ing another file, and objects could be recompiled while the server kept running. The driver supplied built-in functions, efuns, such as write() and move_object(); everything else lived in the mudlib.
LPC had mixed and mapping types well before those were everyday fare. As the LPMud drivers forked, the dialects drifted, so "LPC" meant something slightly different on MudOS than on DGD. One branch left games behind entirely and became µLPC, then Pike, in Linköping.