Difference between a compiled and interpreted programming language?

Compiled Languages

In a compiled language, a special program called a compiler reads the entire source code written by a programmer. This compiler then converts the human-readable code into machine code, which is the low-level instructions that a computer's processor can understand and execute directly. This process creates an executable file.

Characteristics:

• Execution Speed: Generally faster because the translation to machine code happens only once. The resulting executable is optimized for the target machine.
• Error Detection: Many syntax errors are caught during the compilation phase before the program even runs.
• Platform Dependency: The compiled executable is specific to the operating system and processor architecture it was compiled for. To run on a different platform, the code must be recompiled.
• Development Cycle: Involves a distinct compilation step, which can add time to the development process.

Example: Consider a simple C++ program:

#include <iostream>

int main() {
    std::cout << "Hello, World!" << std::endl;
    return 0;
}

Before this program can run, a C++ compiler (like g++) would process this entire file and generate an executable program.

Interpreted Languages

Interpreted languages use an interpreter, which reads the source code and executes it instruction by instruction. There is no separate compilation step that creates a standalone executable. The interpreter translates and runs the code simultaneously.

Characteristics:

• Execution Speed: Typically slower than compiled languages because the translation happens at runtime, for every execution.
• Error Detection: Syntax and runtime errors are often discovered only when the interpreter encounters the problematic line during execution.
• Platform Independence: The source code can often be run on any platform that has a compatible interpreter installed, making them more portable.
• Development Cycle: Often faster for development and debugging due to the lack of a compilation step. Changes can be tested immediately.

Example: Consider a simple Python program:

print("Hello, World!")

When you run this Python script, the Python interpreter reads the print statement, translates it into actions the computer can perform, and then executes those actions.

Hybrid Approaches

It's important to note that the distinction is not always black and white. Some languages, like Java and C#, use a hybrid approach. They are first compiled into an intermediate code (bytecode), which is then interpreted or further compiled by a Just-In-Time (JIT) compiler at runtime. This offers a balance of performance and portability.