COMPILER

What is a compiler?

A compiler is a program that translates a source program written in some high-level programming language (such as Java) into machine code for some computer architecture (such as the Intel Pentium architecture). The generated machine code can be later executed many times against different data each time. The original sequence is usually called the source code and the output called object code. Commonly the output has a form suitable for processing by other programs (e.g., a linker), but it may be a human-readable text file. The name "compiler" is primarily used for programs that translate source code from a high-level programming language to a lower level language (e.g., assembly language or machine language). A compiler is likely to perform many or all of the following operations: lexical analysis, preprocessing, parsing, semantic analysis, code generation, and code optimization.

The first compiler.

The first compiler was written by Grace Hopper, in 1952, for the A-0 programming language. She is also well known for her important role in the development of the COBOL programming language (which is still in widespread use for business applications), including the development of the first COBOL compiler.
The A-0 system, written by her in 1951 and 1952 for the UNIVAC I, was the first compiler ever developed for an electronic computer. The A-0 functioned more as a loader or linker than the modern notion of a compiler. A program was specified as a sequence of subroutines and arguments. The subroutines were identified by a numeric code and the arguments to the subroutines were written directly after each subroutine code. The A-0 system converted the specification into machine code that could be fed into the computer a second time to execute the program.