In computer science, source code (commonly just source or code) is any sequence of statements or declarations written in some human-readable computer programming language. Source code is written in a programming language, which is usually a simplified form of the English language to reduce ambiguity. Source code allows the programmer to communicate with the computer using a reserved number of instructions.

The source code which constitutes a program is usually held in one or more text files, sometimes stored in databases as stored procedures and may also appear as code snippets printed in books or other media. A large collection of source code files may be organized into a directory tree, in which case it may also be known as a source tree.

A computer program's source code is the collection of files needed to convert from human-readable form to some kind of computer-executable form. The source code may be converted into an executable file by a compiler, or executed on the fly from the human readable form with the aid of an interpreter.

The code base of a programming project is the larger collection of all the source code of all the computer programs which make up the project.

Purposes

Source code is primarily used as input to the process that produces an executable program (ie., it is compiled or interpreted). It is also used as a method of communicating algorithms between people (eg., code snippets in books).Fact: date=May 2008

Programmers often find it helpful to review existing source code to learn about programming techniques.Fact: date=May 2008 The sharing of source code between developers is frequently cited as a contributing factor to the maturation of their programming skills.Fact: date=May 2008 Some people consider source code an expressive artistic medium.

Porting software to other computer platforms is usually prohibitively difficult without source code. Without the source code for a particular piece of software, portability is generally very expensive. Binary translation can sometimes be used to run a program when only the executable form rather than the source code is available.

Decompilation can be used to generate source code, either in assembly code or in a high level language.

Programmers frequently adapt source code from one piece of software to use in other projects, a concept known as software reusability.

Organization

The source code for a particular piece of software may be contained in a single file or many files. Though uncommon, a program's source code is not necessarily all written in the same programming language.Fact: date=May 2008 For example, a program written primarily in the C programming language, might have portions written in Assembly language for optimization purposes. It is also possible for some components of a piece of software to be written and compiled separately, in an arbitrary programming language, and later integrated into the software using a technique called library linking. This is the case in some languages, such as Java: each class is compiled separately into a file and linked by the interpreter at runtime.