Incremental-scanning compiler for source-code development system

Abstract

A computer-aided software development system includes programs to implement edit, compile, link and run sequences, all from 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, generating a sequential token list which is saved in memory to be used again where no changes are made; increments of the sequential token list are reused when no changes have been made in the increments and related statements. All of the linking tables are also saved in memory so 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 sequential 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. 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.