Virtual memory management for source-code development system

Abstract

A computer-aided software development system includes programs to implement edit, compile, link and run sequences, all from virtual memory, at very high speed. The compiler operates on an incremental basis, line-by-line, so if only one line is changed in an edit session, then only that line need be recompiled if no other code is affected. Scanning is done incrementally, and the resulting token list saved in memory to be used again where no changes are made. All of the linking tables are saved in virtual memory so that there is no need to generate link tables for increments of code where no changes in links are needed. The parser is able to skip lines or blocks of lines of source code which haven't been changed. All of the source code text modules, the token lists, symbol tables, code tables and related data saved from one compile to another are maintained in virtual memory rather than in files so that speed of operation is enhanced; each module or table is on a separate page with no data from other modules or tables interleaved, and whenever data is added to one of these a reallocation is done to make sure each page has no foreign data. Also, the object code created is maintained in memory rather than in a file, and executed from this memory image, to reduce delays. A virtual memory management arrangement for the system assures that all of the needed data modules and code is present in real memory by page swapping, but with a minimum of page faults, again to enhance operating speed.