The Process of Compilation

The Process of Compilation

Definition of a Compiler

  • A compiler is a specialised computer program which converts source code written in one programming language into another language, commonly machine code or an intermediate language.

Why Do We Need Compilation?

  • Computers cannot directly understand high-level programming languages. They only understand machine language. Hence, converting high-level code to machine code is crucial and this is where the compiler comes in.

Steps in the Compilation Process

  • Lexical Analysis: The compiler will first break up the source code into pieces called tokens. These tokens represent the basic structural parts of the program, for example, identifiers, operators, keywords etc.

  • Syntax Analysis: In this step, the compiler checks that the tokens form meaningful instructions using the rules of the programming language being used.

  • Semantic Analysis: This is the stage where the compiler uses a symbol table to ensure that all identifiers are declared before use, that identifiers are used in appropriate contexts, and other semantic checks.

  • Code Generation: Here, the compiler converts the intermediate or high-level instructions into low-level machine instructions.

  • Optimisation: In the last stage, the compiler looks for ways to make the translated code more efficient. This step is optional and can be conducted at any point in the process.

Types of Compiler

  • Just-In-Time compilers (JIT): These compilers translate the source code into machine code at runtime, allowing for improved performance.

  • Ahead-of-Time compilers (AOT): These compilers convert the source code into machine/executable code before the program is run. This improves runtime performance since no time is spent compiling while the program is in execution.

Advantages of Compilation

  • Efficiency: Compiled programs often run more quickly than interpreted programs, as the translation into machine code happens only once before execution, not at runtime.

  • Binary Distribution: Compiled programs can be distributed as binary files, which are often smaller than source code files.

Disadvantages of Compilation

  • Platform Dependency: Compiled programs are platform-specific. They need to be compiled separately for each platform (OS, chip architecture) that they will run on.

  • Time-Consuming: The compilation process can be quite time-consuming for large programs.

  • Debugging Difficulties: When a program is compiled, information about the original source code is often lost. This makes identifying and fixing errors more challenging than in an interpreted language.