What's the difference between compiled and interpreted language?

What’s the difference between compiled and interpreted language?

The difference is not in the language; it is in the implementation.

Having got that out of my system, here's an answer:

• In a compiled implementation, the original program is translated into native machine instructions, which are executed directly by the hardware.

• In an interpreted implementation, the original program is translated into something else. Another program, called "the interpreter", then examines "something else" and performs whatever actions are called for. Depending on the language and its implementation, there are a variety of forms of "something else". From more popular to less popular, "something else" might be

  • Binary instructions for a virtual machine, often called bytecode, as is done in Lua, Python, Ruby, Smalltalk, and many other systems (the approach was popularized in the 1970s by the UCSD P-system and UCSD Pascal)

  • A tree-like representation of the original program, such as an abstract-syntax tree, as is done for many prototype or educational interpreters

  • A tokenized representation of the source program, similar to Tcl

  • The characters of the source program, as was done in MINT and TRAC

One thing that complicates the issue is that it is possible to translate (compile) bytecode into native machine instructions. Thus, a successful intepreted implementation might eventually acquire a compiler. If the compiler runs dynamically, behind the scenes, it is often called a just-in-time compiler or JIT compiler. JITs have been developed for Java, JavaScript, Lua, and I daresay many other languages. At that point you can have a hybrid implementation in which some code is interpreted and some code is compiled.

Java and JavaScript are a fairly bad example to demonstrate this difference_{, because both are interpreted languages}. Java _{(interpreted)} and C (or C++) _(compiled) might have been a better example.

_{Why the striked-through text? As this answer correctly points out, interpreted/compiled is about a concrete implementation of a language, not about the language per se. While statements like "C is a compiled language" are generally true, there's nothing to stop someone from writing a C language interpreter. In fact, interpreters for C do exist.}

Basically, compiled code can be executed directly by the computer's CPU. That is, the executable code is specified in the CPU's "native" language (assembly language).

The code of interpreted languages however must be translated at run-time from any format to CPU machine instructions. This translation is done by an interpreter.

Another way of putting it is that interpreted _{languages are} code is translated to machine instructions step-by-step while the program is being executed, while compiled _{languages have} code has been translated before program execution.

Here is the Basic Difference between Compiler vs Interpreter Language.

Compiler Language

• Takes entire program as single input and converts it into object code which is stored in the file.
• Intermediate Object code is generated
• e.g: C,C++
• Compiled programs run faster because compilation is done before execution.
• Memory requirement is more due to the creation of object code.
• Error are displayed after the entire program is compiled
• Source code ---Compiler ---Machine Code ---Output

Interpreter Language:

• Takes single instruction as single input and executes instructions.
• Intermediate Object code is NOT generated
• e.g: Perl, Python, Matlab
• Interpreted programs run slower because compilation and execution take place simultaneously.
• Memory requirement is less.
• Error are displayed for every single instruction.
• Source Code ---Interpreter ---Output