Syntax Tree Construction for the Verification of Lexical Analyzer

A Compiler is a language translator which translates high level language to low level language, this is the task of a compiler. Removing the bugs of source program does not assure that the generated target code is completely error free because there may be bugs in compiler also. So it is more important to verify the Compiler itself. Lexical analyzer is a first phase and main part of compiler used for scanning input stream of characters and grouping into tokens. In this paper formal construction of syntax tree is described from the regular expression to verify the lexical analyzer and this is the aim of paper. If the syntax tree will be constructed successfully for the given regular expression then the lexical analyzer will be verified. Formal specifications can be rigorously validated and verified leading to the early detection of specification errors. The specification is described using Model oriented formal specification languages Vienna Development Method (VDM) because only Vienna Development Method provide support for concurrency control and also using VDM Software requirement specification can be automatically converted into computer source code.