Compilers are an essential part of software development. Compilers allow developers to write programs in high-level languages that humans can understand, but then convert that high-level language into a form that only a machine can read.

What Is a Compiler vs. an Interpreter?

Interpreters execute source code line-by-line without compiling it into machine-readable code. As a result, interpreted code runs slower than compiled code and doesn’t generate a machine code file. Alternatively, interpreted programs make it easier to find errors in your code. 


Why Do We Use Compilers?

Programmers use compilers to translate high-level programming languages into machine code that computers can understand and execute.

Compilers play a critical role in the development process because they help catch syntax and semantic errors before we run the code, which saves time and prevents crashes. Compilers also optimize the code for efficient execution and produce faster, more compact programs.

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How Does a Compiler Work?

A compiler analyzes the source code and breaks it down into individual instructions that the computer can understand. In other words, a compiler turns human-readable program code into zeroes and ones.


1. Lexical Analysis

First, the compiler performs a lexical analysis in which it breaks the source code down into a sequence of tokens that represent the individual elements of the program like keywords, operators and identifiers.


2. Syntactic and Semantic Analysis

Next, the compiler performs a syntactic analysis. In this phase, it checks the source code for any syntax errors and ensures that it follows the correct language-specific rules and conventions. If any errors occur, the compiler throws an error and stops the compilation.


3. Optimization

Once the compiler has successfully parsed and checked the source code for errors, it runs low-level optimization on the code to improve its performance. This can involve reducing the amount of memory the program uses or optimizing the code for speed by rearranging instructions or eliminating unnecessary operations.


4. Output Code Generation

Finally, the compiler generates the machine code that corresponds to the original source code. This machine code lives in a binary file that the computer’s hardware can execute directly. 

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Disadvantages of a Compiler

Something to keep in mind here is that compilation makes the code platform-dependent. This means that compiled code produces a machine-readable and machine-specific executable file that only the particular type of machine is able to execute. This means that code compiled on a Windows machine won’t run on a Mac or Linux system without being recompiled.


Compiler Alternative: the Interpreter

Another core tool for running source code is called an interpreter. An interpreter executes source code directly line-by-line, without compiling it into machine code.

Because of the line-by-line interpretation, an interpreted program typically runs slower than compiled code. Also, an interpreted program doesn’t generate a machine code file like compilers do. This means you can’t run an interpreted program independent of the original program. Instead, you have to interpret the program from scratch.

On the other hand, an interpreted program shows potential coding errors line-by-line and one at a time during the interpretation process. This makes finding code errors easier. This is distinct from a compiler, which shows the errors all in one chunk after the compilation, so debugging is a much trickier process.

In programming terminology, it’s said that a programming language is either interpreted or compiled. This isn’t necessarily true. A coding language can have both interpreted and compiled implementations. For example, we usually consider Python an interpreted language, but there’s also a compiled implementation, Cython.

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Should I Use a Compiler or an Interpreter?

The main implication of using an interpreted language like Python is that the code is executed line-by-line, which allows for faster development and easier debugging.

However, interpreted code is generally slower and less efficient than compiled code. Using a compiled language like Cython results in faster code execution and improved performance but the development process is slower and more complex with less flexibility for debugging.

In the case of Python versus Cython, Cython allows for incorporating C code into Python, which results in faster execution times for performance-critical parts of the code, while still providing the benefits of a high-level interpreted language for other parts of the code.

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