A high-level programming language commissioned by NASA in the 1970's. Hal/S is a a real-time aerospace programming language that is most known for use in NASA's Space Shuttle program. Hal/S is used in the programming of onboard shuttle software. Initially Hal/S was a FORTRAN preprocessor then called Hal that was written in FORTRAN and generated FORTRAN source code. In the early 1970's the language was rewritten in XPL and renamed Hal/S.