Definition: Source code

source code
n.
Programming statements and instructions that are written by a programmer. Source code is what a programmer writes, but it is not directly executable by the computer. It must be converted into machine language by compilers, assemblers or interpreters.

Wikipedia says:
Source code (commonly just source or code) is any series of statements written in some human-readable computer programming language. In modern programming languages, the source code which constitutes a program is usually in several text files.

A computer program's source code is the collection of files that can be converted from human-readable form to an equivalent computer-executable form. The source code is either converted into an executable file by a compiler for a particular computer architecture, or executed on the fly from the human readable form with the aid of an interpreter.