C
termprogramming
The language Dennis Ritchie wrote in the early 1970s, in which Unix was rewritten, and in which most operating systems and network stacks are still written.
Its bargain is explicit: enough abstraction to be portable, and nothing between the programmer and the memory. That is why it runs everywhere and why it produced whole vulnerability classes - buffer overflows, use-after-free, and the rest of the memory-safety catalogue that newer languages exist to prevent. Both halves of that sentence are true at once, which is the honest way to read fifty years of C. It is not going away either: too much of the world's running software is written in it for a rewrite to be a plan.
Also known as: C language, K&R