S-algol

S-algol (St Andrews Algol) is a computer programming language derivative of ALGOL 60 developed at the University of St Andrews in 1979 by Ron Morrison and Tony Davie. The language is a modification of ALGOL to contain orthogonal data types that Morrison created for his PhD thesis. Morrison would go on to become professor at the university and head of the department of computer science. The S-algol language was used for teaching at the university at an undergraduate level until 1999. It was also the language taught for several years in the 1980s at a local school in St. Andrews, Madras College. The computer science text Recursive Descent Compiling describes a recursive descent compiler for S-algol, implemented in S-algol. PS-algol is a persistent derivative of S-algol. It was developed around 1981 at the University of Edinburgh and of St Andrews. It supports database ability by providing for longevity of data in the form of a persistent heap that survives termination of PS-algol programs. Ron Morrison's 1979 PhD thesis, On the Development of Algol, describes the design and implementation of the S-algol language. The technical report defining the language, The S-algol Reference Manual (1979, 1988), thanks several people for their help, including David Turner for discussions on language design around 1975. The 1981 computer science text Recursive Descent Compiling describes the compiler implementation and bootstrapping process, and the 1982 book An Introduction to Programming with S-algol uses the language to teach computer programming. The first S-algol implementation was on a PDP-11/40 computer running the Unix operating system. Due to the small 64 kilobyte address space available on the PDP-11, an interpreted bytecode implementation was chosen. A single-pass, recursive descent compiler written in S-algol translated S-algol source into S-code, a bytecode for a stack-based abstract machine tailored for S-algol. The S-code was then executed by an interpreter. The S-algol implementation had many similarities with work on earlier Pascal compilers.