EXECUTABLE

An 'executable' or 'executable file', in computer science, is a file whose contents are meant to be interpreted as a program by a computer.
Most often, it contains the binary representation of machine instructions of a specific processor (in which case the executable may also be referred to as a 'binary')
Whether a file is an executable is mostly a matter of convention; some operating systems designate executable files by specific naming convention (such as the name ending in a filename extension ".bin" or ".exe") or noted alongside the file in its metadata (such as the "execute" permission bits under Unix-like operating systems).

Contents

Modern executables

System calls

Formats

Scripts

Modern executables

On most modern architectures, an executable file contains much information that is not part of the program itself, such as information on the environment required to run the program, debugging and symbolic information, or other housekeeping information used by the operating system to prepare the program to be run.

System calls

Executables contain calls to operating system services in addition to regular machine instructions. This means that executables are usually operating system-specific in addition to being processor-specific.

Formats

COM (.com) (DOS)

PE (.exe, .dll, .ocx, .sys, .scr) (Windows)

ELF (Unix and Unix-like)

Mach-O (Mac)

For a list of more executable formats, see the lists at object file.

Scripts

Main articles: Scripting languages

Not all applications exist in a form readable only by machines. Related, but generally mutually incompatible, are Scripting languages. Unlike binaries, these applications do not go through a compilation step before being delivered to an end user. They are generally human-readable. In a sense, a script exists as both the source code and the "binary" at the same time.