PL/I (pronounced "Programming Language 1") is a programming language that first appeared in 1964. It resembles BASIC and COBOL. This site is bare-bones and uses tables for layout (common before CSS).

However, this compiler is relatively new and still being maintained. v1.4.0 was released yesterday (it added support for array expressions), v1.0 was released in 2023, and development started in 2007.