What is a Compiler?Difference between Compiler/Interpreter

A compiler is familiar among those who are related to the field of computer programming or who develop programming languages. A compiler converts human-written computer language into machine language or code.

It performs many other tasks like detecting or preventing code errors, analyzing syntax, and optimizing the code.If you like to become a software developer or interested in gaining knowledge about computer science, you need to know well about it.

So, in this article, you will know what a compiler is and what are the types of it. What are the uses of it, how do they work and their advantages?

What is a Compiler?

A compiler is a computer program or system software program that translates the source program into a machine program.

This program is used to generate machine code or computer language, that is, it converts high-level programming language into low-level programming language.

It converts source code that is written in many different programming languages, like C, C++, and JavaScript. A compiler is used to optimize code and ensure that the source code executes correctly and that the code is easy for the computer to understand.

It helps ensure that the generated machine code is correct for the hardware being used. It also used to finding errors in source code and fix bugs to perform on a computer without any interruptions.

Use of compilers

Today the whole world is dependent on computers because it is such an intelligent machine which has made even the impossible tasks of people easy. Today there is no area where computers are not used.

But we all know that computer programming plays a big role in making a computer so powerful, because without programming or computer language it is nothing but a lifeless machine.

Because a computer cannot do any work on its own unless it receives instructions. Programming is what instructs a computer what to do.

You may also know that computers do not understand human language. To explain it, instructions have to be given in its own language which we know as machine language. Such as Java, C++, Python, etc. These all are known high-level machine languages that are developed by highly skilled programmers.

You may not know that computers sometimes fail to understand these complex languages because a computer can easily understand only bytecode and from there the role of the compiler starts. It actually works like an interpreter which converts the programming language into machine language so that the computer can understand the instructions exactly what it has to do.

What are the different types of compilers?

Compilers are mainly classified into three types, but they vary in design and functionality:

  • Single Pass
  • Two Pass
  • Multipass

To understand it better, here are some of its common types:

1. Single Pass: It works to translate the entire source code into machine code at once. They do work like syntax, semantic analysis, code generation, etc. However, its ability to check errors is comparatively less because the source code is not analyzed in depth.

2. Two Pass: In this the process of analyzing is divided into two stages and each stage is one pass. In the first pass, only a preliminary analysis of the source code is performed, and data structures and symbol tables are constructed. In the second pass, it generates code based on the information found in the first pass. In this approach, the code is analyzed in depth and the process of optimization takes place on a large scale.

3. Multi-pass: The source code is interpreted in many different sequences to make the program functional. Each interpreter has a specific function and uses the output results as input data for the next process. Unlike single-pass compilers, which interpret the source code only once, multi-pass compilers analyze it in more detail and optimize the code. It explain the source code with a deep analysis of the entire process.

4. Cross-Compiler: They runs on one platform or architecture but generates code for a different platform or architecture. Cross Compiler commonly used to develop software for embedded systems or to target any hardware platform. It enable developers to write code on one machine and compile it for another, to make portability and compatibility.

5. Just-In-Time (JIT): It translates the code just before it is executed, i.e. at runtime. It generates machine code as needed during program execution. It is commonly used in virtual machines (e.g., Java Virtual Machine, .NET Common Language Runtime) and improves performance through optimization.

6. Ahead-of-Time (AOT): AOT compilers translate the code before the program is executed and the entire program is compiled into machine code ahead of time, resulting in a standalone execution. This is especially the case with languages like C and C++, and the compiled code has a different platform.

7. Source-to-Source: Also known as transpiler compilers. These take source code written in one programming language and translate it into code in another equivalent language. It often used for migration purposes, where code is written in a high-level language targeting a particular platform.

8. Optimizing: These work to improve the efficiency of the generated machine code. Optimizing Compilers used various optimization techniques to improve the performance of the code, like loop unrolling, inlining, etc.

How does it work?

As I mentioned before, it is a program that converts the source code written in programming language into machine code which a computer can easily read or understand and can do further work accordingly.

This process of compilation takes place in several different stages, and in this the source code is analyzed in different ways and converted into languages that can be understood by the computer. Below is a brief description of their working process:

1. Lexical Analysis: This is the first part of the collection where they are analyzed literally. This process is called tokenization. In this step, the compiler separates the source code into a stream of tokens. Each token represents a basic element of the language, For example, a keyword, identifier, operator, or punctuation mark.

2. Syntax Analysis: This is the next stage of compilation in which the syntax is analyzed. This is known as parsing. During this, it examine the grammar rules contained in the programming language to form and combine them into statements.

3. Semantic Analysis: In this step, data is extracted from the coded text to interpret the sentences and paragraphs and analyze the grammatical structure to understand and interpret the sentences and paragraphs by identifying relationships with words in a particular context.

4. Intermediate Code Generation: If the program passes all the previous steps, the compiler generates an intermediate code. Although intermediate code is simply a representation of the program that is closer to machine code than the source code, it is still not executable.

5. Optimization: Optimization is the fifth stage of compilation and in this stage, it tries to improve the performance of the intermediate code generated in the previous stage by removing unnecessary instructions, reorganizing the instructions and using more efficient algorithms.

6. Code Generation: Code generation is the last step of compilation and in this step, it converts the intermediate code into machine code. Machine code is a low-level language that a computer processor can easily understand and execute.

What is an interpreter?

An interpreter is a type of program that directly executes source code written in a high-level programming language, translating it into machine code or intermediate code during program execution.

Unlike compilers, which translate the entire source code into machine code before execution, interpreters work line by line, and execute the code sequentially.

The primary role of an interpreter is to directly read, parse, and execute the source code, translating it into machine-understandable instructions when the program runs.

Difference between a Compiler and an Interpreter?

Here’s a table highlighting the key differences between them:

Translation ProcessTranslates the entire program at once.Translates and executes line by line.
OutputGenerates intermediate machine code or executable file.No separate executable file; interprets code directly.
Execution SpeedGenerally faster, as the entire program is translated before execution.Slower, as code is translated and executed line by line.
Memory UsageGenerally more memory-efficient as it produces a standalone executable.May use more memory since it needs to interpret code in real-time.
DebuggingCan be more challenging as debugging is done on the generated machine code.Easier to debug since errors are reported as they occur during interpretation.
PortabilityRequires recompilation for each platform.Portable as it can be executed on any platform with the corresponding interpreter.
ExamplesC, C++, Java.Python, Ruby, JavaScript.
Error DetectionDetects all errors at once during compilation.Detects errors one at a time during interpretation.
Startup TimeSlower startup time as compilation is needed before execution.Faster startup time, as it begins interpreting code without a separate compilation step.
Examples of ImplementationsGCC (GNU Collection), Visual C++.Python Interpreter (CPython), Node.js.
This table shows the key differences between a compiler and an interpreter

Mind it, the choice between a compiler and an interpreter depends on various factors such as the programming language, application requirements, and performance considerations. Some languages, like Java, use a combination of both (Java uses them to generate bytecode, which is then interpreted by the Java Virtual Machine).


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