Systems Programming Language

Systems Programming Language, often shortened to SPL but sometimes known as SPL/3000, was a procedurally-oriented programming language written by Hewlett-Packard for the HP 3000 minicomputer line and first introduced in 1972. SPL was used to write the HP 3000's primary operating system, Multi-Programming Executive (MPE). Similar languages on other platforms were generically referred to as system programming languages, confusing matters.

Originally known as Alpha Systems Programming Language, named for the development project that produced the 3000-series, SPL was designed to take advantage of the Alpha's stack-based processor design. It is patterned on ESPOL, a similar ALGOL-derived language used by the Burroughs B5000 mainframe systems, which also influenced a number of 1960s languages like PL360 and JOVIAL.

Through the mid-1970s, the success of the HP systems produced a number of SPL offshoots. Examples include ZSPL for the Zilog Z80 processor, and Micro-SPL for the Xerox Alto. The later inspired Action! for the Atari 8-bit family, which was fairly successful. The latter more closely followed Pascal syntax, losing some of SPL's idiosyncrasies.

SPL was widely used during the lifetime of the original integrated circuit-based versions HP 3000 platform. In the 1980s, the HP 3000 and MPE were reimplemented in an emulator running on the PA-RISC-based HP 9000 platforms. HP promoted Pascal as the favored system language on PA-RISC and did not provide an SPL compiler. This caused code maintenance concerns, and 3rd party SPL compilers were introduced to fill this need.