First Compiler

Compiler is a computer program (or set of programs) that translates text written in a computer language (the source language) into another computer language (the target language). 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 first compiler was developed in 1952 by Grace Hopper (for the A-0 programming language), a pioneering computer scientist.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.
The FORTRAN team led by John Backus at IBM is generally credited as having introduced the first complete compiler, in 1957.The first compiler for pascal was written on paper by Wirth, who then ran it by hand on itself, and then manually entered the resulting machine code. By dint of attention to detail, he then had a working pascal compiler.