Learn Difference Between Compiler And Interpreter And A Lot More!

Multiple programming languages exist today, but the computer still understands only the binary code i.e., 0 and 1. These programming languages (source code) need to be converted into machine language, i.e., binary code, so that computers may understand them. Here is where interpreters and compilers come in.

Both interpreters and compilers are programs that convert the source code (high-level programming language) into machine-level language through a translation process so that the computers can understand them. Typically, a computer program exists in a high-level programming language that humans can understand. On the contrary, computers don't understand human language at all, but they can easily comprehend programs written in binary code.

Therefore, we first write a computer program in a high-level language, then translate it into binary form, which the computer can read by using interpreters and compilers.

Both interpreter and compiler perform the same function, i.e., convert source code to machine code. Yet, they are different from each other. The major difference between the two is the timing of conversion.

A compiler converts the source code (programming language) to machine code (binary form) before the program is run. On the contrary, an interpreter converts the code at runtime - converting and executing the code line by line, as it's being run.

There are several other differences between the two that we will dive into in this article. But first, let's understand in detail what are compilers and interpreters, their properties, and types in detail. 

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What is a Compiler?

A compiler is a translator that generates an output of a low-level language (i.e., an assembly or machine language) by taking input from a high-level programming language. It is basically a computer program used to convert codes or instructions written in a programming language into machine code (human-readable code to a binary 0 and 1 bits language for a computer processor to understand).

Once the computer has processed the machine code, it performs the corresponding tasks. One condition that a compiler has to follow is the syntax rule of the programming language that is used. If the syntax of the program doesn't match the analysis of the compilers, then there may be errors in the code that must be fixed manually.

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Working of a Compiler

The main function of a compiler is to translate the source code (program) into an object code (machine language). It checks for syntax errors, range/limit violations, etc., and informs the programmer before generating an executable file. It analyzes the entire program and translates it into machine language.

We can categorize the working of a compiler into the following phase:

• Lexical analysis: It is the splitting of source code into an abstract fragment known as lexeme. For each of the lexemes, a token is generated, referring to whether it is a keyword, a string, or some other variable.
• Syntax Analysis: The tokens assigned are structured to form an Abstract Syntax Tree (AST) and the syntax is checked for errors. 
• Semantic Analysis: The Abstract Syntax Tree (AST) is checked for semantic errors. For example, using an undeclared variable, the wrong variable assigned, using keywords as variable, etc.
• Intermediate Code Generation: Two or more intermediate code forms are generated by the process of compilation.
• Optimization: The compilation procedure searches for multiple ways through which the task can be enhanced, i.e., this phase includes code optimizer tasks.
• Code generation: The compiler translates the intermediate optimized code into a machine code, after which the source program is converted to an object program.

Role of a Compiler

• It reads the source codes and generates an executable file.
• It translates programs written in a high-level language into one that the CPU or processor understands.
• The process is comparatively complicated and requires time for analysis. 
• The executable code will consist of machine-specific binary codes.
• Total run time is comparatively long and occupies a large part of the memory. 

Types of Compilers

Compilers can be categorized based on their target language, optimization techniques, and deployment platforms. Some common types of compilers include:

1. Native Compiler: Translates source code directly into machine code for the target processor architecture, producing standalone executable files.
2. Cross-Compiler: Generates code for a different platform or architecture than the one on which it runs, useful for developing software for embedded systems or different operating systems.
3. Just-In-Time (JIT) Compiler: Translates and executes code on-the-fly during runtime, improving performance by dynamically optimizing frequently executed code segments.
4. Ahead-Of-Time (AOT) Compiler: Converts source code into native machine code before execution, commonly used in environments where runtime performance is critical.
5. Interpreter: Executes code line-by-line without generating intermediate machine code, suitable for scripting languages and rapid prototyping.
6. Optimizing Compiler: Applies various optimization techniques to improve the efficiency and performance of generated code, such as loop unrolling, constant folding, and register allocation.
7. Bytecode Compiler: Generates intermediate bytecode, which is then interpreted or further compiled by a virtual machine, commonly used in languages like Java and C#.

These types of compilers serve different purposes and are tailored to specific programming languages, platforms, and performance requirements.

What is an Interpreter?

An interpreter is a program that functions for the translation of a programming language into a comprehensible one. It is a computer program used for converting high-level program statements into machine code. It includes pre-compiled code, source code, etc.

Working of an interpreter

An interpreter works more or less in a similar manner to a compiler. The principal difference between their functioning is that the interpreter does not generate any intermediate code forms. Rather, the program runs simultaneously as it checks for errors. Simply put, it reads the program line by line checking for errors, as the code runs.

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Role of an interpreter

• It translates program statements, line by line, into machine code. 
• It allows modification of the program during execution. 
• Relatively lesser time is consumed for analysis since it runs line by line. 
• Program execution is relatively slow as analysis takes place every time the program is run.

Types of Interpreters

Interpreters can be classified based on their execution model, implementation approach, and deployment environment. Some common types of interpreters include:

1. Single-pass Interpreter: Processes source code sequentially, executing each line or statement as it encounters it, without performing multiple passes over the code.
2. Multi-pass Interpreter: Analyzes the source code multiple times to perform tasks such as parsing, optimization, and execution, potentially improving performance and enabling more sophisticated features.
3. Abstract Syntax Tree (AST) Interpreter: Converts source code into an abstract syntax tree representation before interpretation, allowing for easier manipulation and analysis of program structure.
4. Just-In-Time (JIT) Interpreter: Translates source code into machine code or bytecode during runtime, dynamically optimizing performance by compiling frequently executed code segments.
5. Bytecode Interpreter: Executes intermediate bytecode generated by a compiler, often used in languages like Java and Python, which first compile source code into bytecode for platform-independent execution.
6. Scripting Language Interpreter: Interprets scripting languages such as JavaScript, PHP, and Ruby, providing dynamic runtime execution and facilitating rapid development and prototyping.
7. Embedded Interpreter: Integrated into another application or system to provide scripting capabilities, allowing users to extend functionality through custom scripts or plugins.

These types of interpreters serve different purposes and are tailored to specific programming languages, runtime environments, and performance requirements.

Difference between Compiler and Interpreter

The basic difference between compilers and interpreters can be summarized as follows:

Compiler vs Interpreter: Frequently Asked Questions

1. Which is faster - a compiler or an interpreter?

In general, compilers tend to produce faster-running programs compared to interpreters. This is because compilers translate the entire source code into machine code or bytecode before execution, allowing for optimizations and producing an executable file. On the other hand, interpreters process source code line-by-line during runtime, which can lead to slower execution as the code is translated and executed simultaneously.

However, Just-In-Time (JIT) compilers, which dynamically compile code during runtime like interpreters, can achieve performance levels closer to compiled code by applying optimizations on the fly. Ultimately, the speed difference between compilers and interpreters depends on various factors, including the language, implementation, and optimization techniques used.

2. Are there any similarities between a compiler and an interpreter?

Yes, there are several similarities between a compiler and an interpreter. These are listed below:

• Translation: Both are used to convert source code into machine code.
• Debugging codes through error detection: Both display error messages. A compiler displays errors after compiling, while an interpreter displays errors line-by-line when translating the code. This allows programmers to identify the errors in their code and fix them. Thus, both help programmers debug their codes.
• Portability: Both interpreters and programmers aid in the portability of the code. The code generated by the interpreter and the compiler is not dependent on the platform in which it was executed. And thus, it can be ported across different platforms.

3. Can you give some examples of interpreted languages?

Some popular interpreted languages are Python, Ruby, Perl, PHP, and JavaScript.

4. Can you share some examples of compiled languages?

Some popular compiled languages are C, C#, Java, C++, and Go.

5. Is it better to use a compiler or an interpreter?

The answer to this question depends on the user's and/or application's requirements. If speed is the need of the hour, then the compiler is the way to go. However, if flexibility is the core requirement in an application, then an interpreter is a better choice. 

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