IMPLEMENTATION OF CSP : A COMPILER FOR A SUBSET OF PASCAL

Abstract

A Compiler for a Subset of Pascal (CSP) has been designed and then implemented. CSP is developed in Turbo Pascal ..Language. The only tool used in the development of CSP is the Turbo Pascal Compiler.This work is divided into various major compilation tasks, viz., lexical analysis, syntax analysis, scope analysis, type analysis, and code generation & optimization, i.e., CSP has been developed in a phased manner. CSP has been designed to act as an efficient multipass compiler. It is divided into a series of passes known as Scanner (Pass 1), Parser (Pass 2), and Code Optimizer (Pass 3). Each pass need to be loaded once only to perform a partial compilation of the whole program. The passes are loaded in computer's memory in their natural order beginning with Pass 1. The passes are supervised by an administrator, i.e.;' the main program. The temporary files are deleted at the end of the compilation. If errors are detected in a program, the compiler outputs these error messages in the output window and generates no code. The error handling and recovery routines have been included in Pass 2. After outputting the first error of an erroneous line, the parser skips that line, so as to avoid, a burst of redundant error messages relating to that line, that might appear. These superfluous messages are suppressed by a simple and effective method, inbuilt in the parser. The scanner uses hashing with direct chaining to perform search and insert operations on the symbol table prepared by it. The parser uses recursive descent method of parsing. The code optimizer optimizes the postfix code, generated by the parser.