Compiler

A compiler is a program that converts source code (in a programming language) to a machine language form (object code) that a computer can execute. Some compilers output assembly language which is then converted to machine language by a separate assembler.

Description
A compiler is distinguished from an assembler by the fact that each input statement does not, in general, correspond to a single machine instruction or fixed sequence of instructions. A compiler may support such features as automatic allocation of variables, arbitrary arithmetic expressions, control structures such as FOR and WHILE loops, variable, input/ouput operations, s and of source code.

History
, written by for the  in 1952, is considered to be one of the first primitive compilers. The, written around the same time for the , was one of the first working algebraic compilers. Steve Wozniak, when writing Integer BASIC for the Apple I in 1975-1976, had to the instructions directly into machine language for the MOS 6502 processor because he could not afford a compiler at the time.

Compilers used by Apple
Integrated development environments (IDEs) provided by Apple for their operating systems typically include a compiler.
 * Macintosh Programmer's Workshop (MPW), for classic Mac OS.
 * CodeWarrior (from Metrowerks), for PowerPC.
 * Xcode, for iOS, iPadOS, macOS (formerly Mac OS X), tvOS, and watchOS.