SAL: systems assembly languages

Abstract

The Cambridge Computer-Aided Design group is writing some general purpose software tools that aim to assist scientists and engineers to apply their problems to the computer with maximum ease. These tools include a storage allocation system, a data structure package, a compiler-compiler for mixed graphical/verbal on-line languages, a package of procedures for generating pictures and transmitting them to a display, plotter, or file, and programs for operating a link between a multiaccess computer and a satellite computer. When the group started late in 1965 it had to determine what language to use to write these systems. After struggling with the difficulties of assembly code for some time for those programs for which FORTRAN was unsuitable, we decided to design and implement a more suitable language; Systems Assembly Language (SAL) is the result. The purpose of this article is to explain the thinking behind SAL rather than to expound on the finer details of the language itself. We feel that this type of language which combines the freedom and flexibility of assembly code with many of the facilities normally associated with high level languages, could be useful to many other workers. Further, this type of language could perhaps usefully be provided on all computers.