Compiler Design and Construction - Old Questions

1.  What do you mean by compiler? Explain the semantic analysis phase of compiler construction.

A compiler is a program that takes a program written in a source language and translates it into an equivalent program in a target language. As an important part of a compiler is error showing to the programmer.

Block diagram for phases of compiler:

In Semantic Analysis phase, the semantic analyzer checks the source program for semantic errors and collects the type information for the code generation. Semantic analyzer checks whether they form a sensible set of instructions in the programming language or not. Type-checking is an important part of semantic analyzer. 

Semantic analyzer is required when the compiler may require performing some additional checks such as determining the type of expressions and checking that all statements are correct with respect to the typing rules, that variables have been properly declared before they are used, that functions are called with the proper number of parameters etc. This semantic analyzer phase is carried out using information from the parse tree and the symbol table.

Example: