Understanding High-Level Languages: Compiler vs. Interpreter
In the previous lecture, we discussed the types of programming languages—low-level and high-level languages. Now, let us explore high-level languages further.
High-level languages can be categorized as either compiler-based, interpreter-based, or hybrid. But what does this mean?
Why Do We Need Translators?
High-level languages resemble human languages, making them easier for programmers to read and write. However, machines cannot understand these languages directly. Therefore, high-level language programs must be translated into machine language. This translation is done either by a compiler or an interpreter.
Methods of Translation
There are two main methods of translation:
Compiler-based translation
Interpreter-based translation
Certain languages use only compilers, some use only interpreters, and some use both (hybrid).
Categories of High-Level Languages
Compiler-Based Languages – These languages use a compiler for translation.
Examples: C, C++
The compiler translates the entire program into machine code before execution.
Interpreter-Based Languages – These languages use an interpreter for translation.
Examples: PHP, JavaScript
The interpreter translates and executes the code line by line.
Hybrid Languages – These languages use both a compiler and an interpreter.
Examples: Python, Java, C# (Dotnet languages)
They first compile the code into an intermediate form and then interpret it at runtime.
Compiler vs. Interpreter
What is a Compiler?
A compiler translates the entire program into machine code before execution. Let’s take an example of a C program:
The program file (
program.c
) contains source code written in C.A compiler translates the C code into machine code, generating an executable file (
program.exe
).The machine executes this compiled file.
Key Characteristics of a Compiler:
Translates the entire program at once.
Generates a separate machine code file.
If there are errors, translation stops until they are fixed.
Translation occurs only once; the generated machine code can be executed multiple times without re-translation.
Compiler-based languages are generally faster because translation happens only once.
What is an Interpreter?
An interpreter translates and executes code line by line. Let’s consider JavaScript as an example:
The program file contains JavaScript code.
The interpreter reads the first line, converts it to machine code, and executes it immediately.
The process repeats for each subsequent line.
Key Characteristics of an Interpreter:
Translates code line by line.
No separate machine code file is generated.
The program must be interpreted every time it runs.
Execution is slower because translation occurs at runtime.
Interpreter-based languages are more flexible and provide a runtime environment (e.g., JavaScript runs inside the browser).
Which One is Better?
In terms of speed, compiler-based languages are faster because they translate the program once. However, interpreter-based languages are more flexible and easier to debug.
How Hybrid Languages Work
Hybrid languages combine the best features of both compilers and interpreters. For example:
Python first compiles the source code into an intermediate bytecode.
This bytecode is then executed by an interpreter.
Java follows a similar approach using the Java Virtual Machine (JVM).
C# compiles code into an intermediate language (IL), which is then interpreted by the .NET runtime.
Modern Enhancements: JIT Compilation
To improve the performance of interpreted languages, modern interpreters use Just-In-Time (JIT) compilation. JIT compilers convert entire code blocks into machine code before execution, making interpretation faster.
Conclusion
We now understand the fundamental differences between compilers and interpreters:
Compilers translate the whole program before execution.
Interpreters translate and execute code line by line.
Hybrid languages use a combination of both.
In the next lecture, we will explore hybrid languages in detail, focusing on how Python, Java, and C# work efficiently using both compilation and interpretation.
Stay tuned!