Interpreter

What is an Interpreter?

An interpreter is a computer program that is used to directly execute program instructions written using one of the many high-level programming languages without needing to compile the program first.

Key Takeaways

Programming languages are implemented in two ways: interpretation and compilation.
Compilers and interpreters can be used in conjunction.
The interpreter transforms the high-level program into an intermediate language that it executes.
Programming languages that use interpreters include Python, Ruby, and JavaScript.
An interpreter is useful for scripting and other small programs.

Table of Contents Table of Contents

What is an Interpreter?
Key Takeaways
How Does an Interpreter Work?
6 Types of Interpreters
Interpreter vs. Compiler
Interpreter Applications
Interpreter Pros and Cons
The Bottom Line
FAQs

Table of Contents

What is an Interpreter?
Key Takeaways
How Does an Interpreter Work?

Show Full Guide

6 Types of Interpreters
Interpreter vs. Compiler
Interpreter Applications
Interpreter Pros and Cons
The Bottom Line
FAQs

How Does an Interpreter Work?

What does an interpreter do in programming? As the name suggests, an interpreter transforms or interprets a high-level programming code into code that can be understood by the machine, also called machine code, or into an intermediate language that can be easily executed as well.

The interpreter reads each statement of code and then converts or executes it directly. In contrast, an assembler or a compiler converts a high-level source code into native, compiled code that can be executed directly by the operating system (OS) (e.g., create a exe program).

Both compilers and interpreters have their advantages and disadvantages and are not mutually exclusive; this means that they can be used in conjunction, as most integrated development environments employ both compilation and translation for some high-level languages.

In most cases, a compiler is preferable since its output runs much faster compared to a line-by-line interpretation. Rather than scanning the whole program and translating it into machine code like a compiler does, the interpreter translates code one statement at a time.

While the time to analyze source code is reduced, especially a particularly large one, execution time for an interpreter is comparatively slower than a compiler. On top of that, since interpretation happens per line or statement, it can be stopped in the middle of execution to allow for either code modification or debugging.

Compilers must generate intermediate object code that requires more memory to be linked, contrary to interpreters which tend to use memory more efficiently.

Since an interpreter reads and then executes code in a single process, it is very useful for scripting and other small programs. As such, it is commonly installed on Web servers, which run a lot of executable scripts. It is also used during the development stage of a program to test small chunks of code one by one rather than having to compile the whole program every time.

Every source statement is executed line by line during execution, which is particularly appreciated for debugging purposes because it allows for immediate error recognition. Interpreters are also used for educational purposes since they can be used to show students how to program one script at a time.

6 Types of Interpreters

Bytecode interpreter.
Threaded code interpreter.
Abstract syntax tree (AST) interpreter.
Just-in-time (JIT) compilation.
Read-eval-print loop (REPL) interpreter.
Tree-walk interpreter.

Interpreter vs. Compiler

Interpreter

Executes code line by line
Slower execution
Efficient memory usage
Used by PHP, Python, Ruby, JavaScript

Compiler

Compiles entire code at once
Faster execution
Requires more memory for object code
Used by C, C++, Pascal, Java

Interpreter Applications

Interpreters in VoIP servicesInterpreters in web browsersInterpreters in game development

VoIP services and systems handle commands, such as session initiation and protocol adjustments, in real-time, often through scripting languages (e.g., JavaScript, Python) that use interpreters to manage and execute code dynamically.

Web browsers use JavaScript interpreters to run JavaScript code directly on the client-side, enabling interactive elements and responsive web design (RWD). The result is an instant response to actions without reloading the page.

Game engines use interpreters for scripting languages to manage game events, AI behavior, and user interactions. This enables developers to make quick changes and test new features without recompiling the entire game.

Interpreter Pros and Cons

Pros

Allows code to run on different systems without modification
Faster debugging by executing code line-by-line, making it easier to identify errors
Generally, use less memory than compiled code
Provides immediate feedback on code changes, speeding up the testing process

Cons

Interpreted code usually runs slower than compiled code
Less efficient for large programs
Higher security risk as malicious code can be run dynamically
Not suitable for all languages – some rely on compilation for execution

The Bottom Line

The interpreter definition refers to a computer program used to directly execute program instructions written using a high-level programming language. The interpreter reads each statement of code and then executes it directly.

Unlike a compiler, which translates the entire program into machine code in one go, an interpreter processes each statement or line individually, making it valuable for tasks requiring immediate feedback, such as debugging and scripting.

Commonly used in languages like Python, Ruby, and JavaScript, interpreters enable real-time code adjustments and efficient memory usage, although it may result in slower execution compared to compiled languages like Java or C++.