A structure editor has proved to be useful in preserving the syntactic correctness and supporting the semantic analysis of programs during a program editing session. In this thesis, a type checker for a program editor based on the attribute grammar has been developed. It uses links between the declaration and the use of symbols in a program in addition to the attributes information. This greatly enhances the efficiency of type checking in an interactive editing environment. The structure of the symbol table has been expanded to provide more informative facts such as the list of declared our undeclared symbols and the number of the uses of each symbol in a program.
