compiler (redirected from compiling program)

compiler

Computer software that translates (compiles) source code written in a high-level language (e.g., C++) into a set of machine-language instructions that can be understood by a digital computer's CPU. Compilers are very large programs, with error-checking and other abilities. Some compilers translate high-level language into an intermediate assembly language, which is then translated (assembled) into machine code by an assembly program or assembler. Other compilers generate machine language directly.

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(1) Software that converts a set of high-level language statements into a lower-level representation. For example, a help compiler converts a text document embedded with appropriate commands into an online help system. A dictionary compiler converts terms and definitions into a dictionary lookup system.

(2) Software that translates a program written in a high-level programming language (C/C++, COBOL, etc.) into machine language. A compiler usually generates assembly language first and then translates the assembly language into machine language. A utility known as a "linker" then combines all required machine language modules into an executable program that can run in the computer. See optimizing compiler.

The following is a conceptual example of source code being converted to machine language by the compiler:

 Source Code   Assembly Language  Machine Language
 IF COUNT=10   Compare A to B     Compare 3477 2883
  GOTO DONE    If equal go to C   If = go to 23883
   ELSE        Go to D            Go to 23343
  GOTO AGAIN
 ENDIF
            Actual Machine Code (simulated)
            10010101001010001010100
            10101010010101001001010
            10100101010001010010010

From C to Assembly Language

A C/C++ compiler converts C and C++ code into assembly language as shown in this example. The red arrows point to various function calls, and the assembly code to perform those calls follows each statement.

Compilers and Interpreters

Compiled programs (right) are translated into the machine language of the target computer. Interpreted programs (left and center) are either kept in their original source code or are precompiled into an intermediate form. In both cases, an interpreter is required to translate the program into machine language at runtime, whereas the compiled program is "ready to go."

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(programming, tool)

compiler - A program that converts another program from some source language (or programming language) to machine language (object code). Some compilers output assembly language which is then converted to machine language by a separate assembler. 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 scope, input/ouput operations, higher-order functions and portability of source code. AUTOCODER, written in 1952, was possibly the first primitive compiler. Laning and Zierler's compiler, written in 1953-1954, was possibly the first true working algebraic compiler. See also byte-code compiler, native compiler, optimising compiler.