What are the key components of a typical compiler?

A typical compiler consists of key components such as lexical analyser, syntax analyser, semantic analyser, intermediate code generator, code optimiser, and code generator.

The first stage of a compiler is the lexical analyser, also known as the scanner. This component reads the source program, character by character, and converts it into a series of tokens. Tokens are the smallest meaningful units of the program, such as keywords, identifiers, operators, and punctuation symbols. The lexical analyser also removes white spaces and comments from the source program.

The next component is the syntax analyser or parser. It takes the tokens produced by the lexical analyser and groups them into grammatical phrases that are used by the compiler to synthesise output. It checks the expressions, statements, and program units to ensure that they follow the syntax of the programming language. If the syntax analyser finds any syntax errors, it generates error messages.

The semantic analyser then checks the parsed code for semantic errors. It ensures that the statements and expressions in the program are meaningful. For example, it checks that variables are declared before they are used, that the types of expressions are compatible, and that functions are called with the correct number and types of arguments.

The intermediate code generator translates the source program into an intermediate language that is easier for the compiler to manipulate than the original source language. This intermediate code is a low-level representation of the source program, but it is not specific to any particular machine.

The code optimiser improves the intermediate code so that the resulting machine code runs more efficiently. It removes redundant code, performs loop optimisation, and rearranges computations to make the program run faster or take up less space.

Finally, the code generator translates the optimised intermediate code into the target machine language. It allocates memory for variables and generates machine instructions. The output of the code generator is the object code, which can be linked with other object code modules and executed on the machine.

In summary, a compiler is a complex piece of software that translates a program written in a high-level language into a low-level machine language. It consists of several components, each of which performs a specific task in the compilation process.