C
Systems programming language. Dennis Ritchie, Bell Labs, 1972. Created to rewrite Unix in a higher level than assembly. The lingua franca of OSes, compilers, embedded, runtimes.
K&R C (1978 book), ANSI C (C89/C90), C99, C11, C17, C23 (2024). Minimal core: 32 keywords. Manual memory management = the source of most security holes over 50 years (buffer overflow, use-after-free). Modern counter-movement: Rust for systems. Despite that, C still dominates the Linux kernel, embedded, runtime libraries (libc), Postgres, SQLite. Will never die.