Compiled vs. Interpreted Languages

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I'm trying to get a better understanding of the difference. I've found a lot of explanations online, but they tend towards the abstract differences rather than the practical implications.

Most of my programming experiences has been with CPython (dynamic, interpreted), and Java (static, compiled). However, I understand that there are other kinds of interpreted and compiled languages. Aside from the fact that executable files can be distributed from programs written in compiled languages, are there any advantages/disadvantages to each type? Oftentimes, I hear people arguing that interpreted languages can be used interactively, but I believe that compiled languages can have interactive implementations as well, correct?

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13 Answers

This is one of the biggest misunderstood things in computer science as I guess. Because interpretation and compilation are completely two different things, which we can't compare in this way.

The compilation is the process of translating one language into another language. There are few types of compilations.

  • Compiling - Translate high-level language into machine/byte code (ex: C/C++/Java)
  • Transpiling - Translate high-level language into another high-level language (ex: TypeScript)

Interpretation is the process of actually executing the program. This may happen in few different ways.

  • Machine level interpretation - This interpretation happens to the code which is compiled into machine code. Instructions are directly interpreted by the processor. Programming languages like C/C++ generate machine code, which is executable by the processor. So the processor can directly execute these instructions.

  • Virtual machine level interpretation - This interpretation happens to the code which is not compiled into the machine level (processor support) code, but into some intermediate-level code. This execution is done by another software, which is executed by the processor. At this time actually processor doesn't see our application. It just executing the virtual machine, which is executing our application. Programming languages like Java, Python, C# generate a byte code, which is executable by the virtual interpreter/machine.

So at the end of the day what we have to understand is, all the programming languages in the world should be interpreted at some time. It may be done by a processor(hardware) or a virtual machine.

The compilation is just the process of bringing the high-level code we write that is human-understandable into some hardware/software machine-understandable level.

These are completely two different things, which we can't compare. But that terminology is pretty much good to teach beginners how programming languages work.

PS:
Some programming languages like Java have a hybrid approach to do this. First, compile the high-level code into byte code which is virtual-machine readable. And on the fly, a component called the JIT compiler compiles byte-code into machine code. Specifically, code lines that are executed again and again many times are get translated into the machine language, which makes the interpretation process much faster. Because hardware processor is always much faster than virtual interpreter/processor.

How Java JIT compiler works

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Short (un-precise) definition:

Compiled language: Entire program is translated to machine code at once, then the machine code is run by the CPU.

Interpreted language: Program is read line-by-line and as soon as a line is read the machine instructions for that line are executed by the CPU.

But really, few languages these days are purely compiled or purely interpreted, it often is a mix. For a more detailed description with pictures, see this thread:

What is the difference between compilation and interpretation?

Or my later blog post:

https://orangejuiceliberationfront.com/the-difference-between-compiler-and-interpreter/

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