Experience with access functions in an experimental compiler

This paper describes an access function subsystem embedded in portions of an experimental microcode compiler which was built and used during 1973--6 using the IBM PL/I optimizing compiler under VM/370 and CMS. The use of the access function subsystem in this context was itself an experiment, performed by a group for all of whom PL/I was a new language and VM/370 a new operating system. The implementation of the subsystem was done strictly within the confines of the PL/I language. The basic objectives were ease of use, provision of a focal point for global storage management, extensive run-time validity checking with appropriate diagnostics, and data protection. Beyond satisfying these objectives, the subsystem proved more valuable than anticipated due to positive contributions made to debugging code in the VM/370 interactive development environment.