Compiler Design and Construction - Old Questions

1.  What do you mean by compiler? How source program analyzed? Explain in brief.

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.

Analysis phase breaks up the source program into constituent pieces and creates an intermediate representation of the source program. Analysis of source program includes: lexical analysis, syntax analysis and semantic analysis.

1. Lexical Analysis:

In this phase, lexical analyzer reads the source program and returns the tokens of the source program. Token is a sequence of characters that can be treated as a single logical entity (such as identifier, operators, keywords, constants etc.).

2. Syntax Analysis:

In this phase, the syntax analyzer takes the token produced by lexical analyzer as input and generates a parse tree as output. In syntax analysis phase, the parser checks that the expression made by the token is syntactically correct or not, according to the rules that define the syntax of the source language.

3. Semantic Analysis:

In this 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.

Example of Analysis phase: