20 min read

Translators: Assemblers, Compilers and Interpreters

Why programs must be translated into machine code, and how assemblers, compilers and interpreters differ.

Why Translation Is Needed

The CPU only understands machine code . Anything written in assembly or a high-level language (the source code) must be translated into machine code (the object code) before it can run. A translator is a program that does this.

Compiling vs interpreting

A compiler translates once, ahead of time. An interpreter translates as the program runs.

Compiler vs interpreter

$Compiler$	$Interpreter$
$Translates the whole program before it runs$	$Translates and runs one statement at a time$
$Reports all errors after compiling; nothing runs until they are fixed$	$Stops at the first error it reaches — useful while learning$
$Produces an executable file; the source code is not needed to run it$	$No separate executable; the interpreter and source are needed every time$
$Compiled program runs fast$	$Usually runs more slowly$
$Examples: C, C++, Go$	$Examples: Python, JavaScript (in the browser), PHP$

Practice

Which translator translates and runs a program one statement at a time?

Why Translation Is Needed

The CPU only understands machine code . Anything written in assembly or a high-level language (the source code) must be translated into machine code (the object code) before it can run. A translator is a program that does this.

Three Kinds of Translator

Compiling vs interpreting

A compiler translates once, ahead of time. An interpreter translates as the program runs.

Compiler vs interpreter

$Compiler$	$Interpreter$
$Translates the whole program before it runs$	$Translates and runs one statement at a time$
$Reports all errors after compiling; nothing runs until they are fixed$	$Stops at the first error it reaches — useful while learning$
$Produces an executable file; the source code is not needed to run it$	$No separate executable; the interpreter and source are needed every time$
$Compiled program runs fast$	$Usually runs more slowly$
$Examples: C, C++, Go$	$Examples: Python, JavaScript (in the browser), PHP$

Practice

Which translator translates and runs a program one statement at a time?