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?
Compilers translate code from a high-level programming language into machine code before the program runs. Interpreters, on the other hand, execute high-level code line-by-line at runtime, typically without producing a separate machine code file. Because of this, interpreted programs often run slower but make it easier to identify errors during execution.
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 many 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.
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 machine code.
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. Syntax Analysis
Next, the compiler performs a syntax analysis, also known as parsing. 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. Semantic Analysis
During semantic analysis, the compiler ensures that the code’s logic is valid. This can involve checking if data types are used properly or if there are any undeclared variables in the code.
4. Intermediate Code Generation
After semantic analysis, most compilers translate source code into an intermediate representation (IR). This IR is a low-level, machine-independent code that lies between the high-level source code and the final machine code. Generating IR code allows the compiler to perform optimizations more effectively before generating machine-specific code.
5. Code Optimization
Once the compiler has generated an intermediate representation, it runs low-level optimization on this code to improve its performance. This may include removing redundant code, improving memory access patterns or safely rearranging instructions to improve performance without altering program behavior.
6. 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.
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. For example, code compiled on a Windows machine typically won’t run on a Mac or Linux system without being recompiled.
Compiler vs. 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. Unlike compiled programs, interpreted code requires the interpreter to be present at runtime to execute the program.
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.
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.
Frequently Asked Questions
What is a compiler?
A compiler is a program that translates high-level programming code into machine-readable code that a computer can execute. It can help catch errors, optimize performance and generate a binary file that runs on a specific platform.
What is the difference between a compiler and an interpreter?
A compiler translates code into machine code before execution, while an interpreter runs code line-by-line without generating a separate machine file.
What are the main phases of compilation?
The main phases of code compilation are:
- Lexical analysis
- Syntax analysis
- Semantic analysis
- Intermediate code generation
- Code optimization
- Output or target code generation
