What Is a Compiler? Definition, Types, Functions & Examples

What Is a Compiler?

A compiler is a software designed to translate or convert source code into object code that can be understood by a machine.

In short, this software serves as a crucial bridge connecting programmers with the computer hardware.

With such software tools, high-level programming languages can be transformed into machine language, making it easier for computers to process. This process is commonly referred to as compilation.

Compiler Function

In general, this software is responsible for assisting programmers in converting program code. However, it also serves several other functions, including:

• Translating program code to enable it to run on different platforms.
• Facilitating programmers in checking syntax errors in the source code of a program.
• Simplifying debugging with specialized features.
• Assisting in optimizing the resulting code and machine instructions to enhance program performance.
• Improving the speed of the compilation process by translating only the modified parts of the code (incremental technique).
• Enhancing the cyber security of a program by validating the source code.

Compiler and Interpreter, What’s the Difference?

After understanding what is a compiler and its functions, you may find that the concept is similar to something called an interpreter. However, both of them have quite significant differences, such as:

• Definition: An interpreter is a program that helps interpret commands in a high-level language into a simpler language. On the other hand, a compiler is software that translates source code to make it understandable for the machine.
• Commands: Commands in an interpreter are generally interpreted line by line. In contrast, commands in a compiler are translated simultaneously.
• Linker: An interpreter does not require a linker, while a compiler needs a linker.
• Program Code: A compiler can conceal the program code (e.g., Fortran, Cobol, Pascal, etc.). On the other hand, an interpreter cannot conceal the code (e.g., ASP, Perl, PHP).

How Compiler Works?

Essentially, the operation varies depending on the method used to analyze and convert the source code. However, regardless of the approach, here are some common stages you need to know:

Analysis Phase

In this stage, the compiling software is responsible for reading the source code, analyzing the data structure, and interpreting the meaning of the code. The stages include:

• Lexical Analysis: It divides the source code into individual code fragments representing specific patterns. These code fragments are then prepared for further analysis in terms of syntax and semantics.
• Syntax Analysis: It verifies the code's compliance with the rules of the programming language in the source code.
• Semantic Analysis: It checks the validity, logic, and accuracy of the code. It also examines whether variables have been categorized into the appropriate types.

Synthesis Phase

After the analysis process is complete, the next phase is the synthesis phase. In this stage, this compiling software will generate two types of code: object code and intermediate code.

• Intermediate Representation (IR) Generation: After the source code passes through the analysis phases mentioned above, it will then produce intermediate representation (IR), facilitating the translation of the source code into another format.
• Code Optimizer: It runs this process by optimizing the IR code to be ratified as the final code. Note that some types also allow users to manually perform these optimizations.
• Output Code Generation: This is the final stage where it produces the final code in the form of optimized IR code.

Upon completion of the synthesis phase, the compiler then generates an executable file that can be directly run by the computer.

Compiler Types

In general, this software can be categorized into four different types. They are: 

1. Bootstrap 

This type can generate the latest version of specific software, making them widely used for improving and optimizing performance.

2. Cross Compiler

This type is suitable for developing cross-platform software as it can produce abstract code that can be used on different operating systems from the parent platform itself.

3. Transcompiler (Source-to-Source)

Transcompilers can convert source code originating from a High-Level Language (HLL) into another programming language (non-machine code).

4. Decompiler

Decompilers can convert machine code into program source code. This type is commonly used to support learning practices related to programming.

Compiler Examples in Some Programming Languages 

Once you understand what is a compiler, its functions, types, and how it works, it's essential to know which programming languages can utilize this software. Here are some of them:

1. C++

C++ is a programming language that allows developers to write code with a high level of control while maintaining flexibility. Some commonly used software for C++ are Visual C++ and GCC.

2. Java

Java also uses a compiler as part of its software development cycle. As one of the most popular and secure programming languages, Java employs specific software to transform program code into bytecode. Some compiler examples in Java are OpenJDK, IBM SDK, and Oracle JDK.

3. Visual Basic

Visual Basic is a programming language for rapid application development. When using Visual Basic, the source code is converted by the Visual Basic Compiler (VBC).

4. Kotlin

This programming language is commonly used for developing Android applications due to its object-oriented nature. Some suitable compiling software for Kotlin are Studio and the Kotlin Compiler.

5. Pascal

Pascal is a suitable programming language for creating applications with a structural programming language. If you are using Pascal, the required software is the Pascal Compiler.