PATH (variable) - DOS, OS/2, and Windows

DOS, OS/2, and Windows

On DOS, OS/2, and Windows operating systems, the %PATH% variable is specified as a list of one or more directory names separated by semicolon (;) characters.

The Windows system directory (typically C:\WINDOWS\system32) is typically the first directory in the path, followed by many (but not all) of the directories for installed software packages. Many programs do not appear in the path as they are not designed to be executed from a command window, but rather from a Graphical User Interface. Some programs may add their directory to the front of the PATH variable's content during installation, to speed up the search process and/or override OS commands. In the DOS era, it was customary to add a PATH {program directory};%PATH% or SET PATH={program directory};%PATH% line to AUTOEXEC.BAT.

When a command is entered in a command shell or a system call is made by a program to execute a program, the system first searches the current working directory and then searches the path, examining each directory from left to right, looking for an executable filename that matches the command name given. Executable programs have filename extensions of EXE or COM, and batch scripts have extensions of BAT or CMD. Other executable filename extensions can be registered with the system as well.

Once a matching executable file is found, the system spawns a new process in which to run it.

The PATH variable makes it easy to run commonly used programs located in their own folders. If used unwisely, however, the value of the PATH variable can slow down the operating system by searching too many locations, or invalid locations.