or is one of the

environment variable An environment variable is a dynamic-named value that can affect the way running processes will behave on a computer. They are part of the environment in which a process runs. For example, a running process can query the value of the TEMP envi ...

s used in

DOS DOS is shorthand for the MS-DOS and IBM PC DOS family of operating systems. DOS may also refer to: Computing * Data over signalling (DoS), multiplexing data onto a signalling channel * Denial-of-service attack (DoS), an attack on a communicat ...

OS/2 OS/2 (Operating System/2) is a series of computer operating systems, initially created by Microsoft and IBM under the leadership of IBM software designer Ed Iacobucci. As a result of a feud between the two companies over how to position OS/2 ...

and

Windows Windows is a group of several proprietary graphical operating system families developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. For example, Windows NT for consumers, Windows Server for serv ...

, which normally points to the

command line interpreter A command-line interpreter or command-line processor uses a command-line interface (CLI) to receive commands from a user in the form of lines of text. This provides a means of setting parameters for the environment, invoking executables and pro ...

, which is by default in DOS, Windows 95, 98, and ME or in OS/2 and

Windows NT Windows NT is a proprietary graphical operating system An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs. Time-sharing operating systems sc ...

. The variable name is written in all-uppercase under DOS and OS/2. Under Windows, which also supports lowercase environment variable names, the variable name is inside the DOS emulator

NTVDM Virtual DOS machines (VDM) refer to a technology that allows running 16-bit/32-bit DOS and 16-bit Windows programs when there is already another operating system running and controlling the hardware. Overview Virtual DOS machines can operate eit ...

and for any DOS programs, and under CMD.EXE. The variable's contents can be displayed by typing or at the command prompt. The environment variable by default points to the full

path A path is a route for physical travel – see Trail. Path or PATH may also refer to: Physical paths of different types * Bicycle path * Bridle path, used by people on horseback * Course (navigation), the intended path of a vehicle * Desire p ...

of the command line interpreter. It can also be made by a different company or be a different version. Another use of this environment variable is on a computer with no hard disk, which needs to boot from a floppy disk, is to configure a ram disk. The COMMAND.COM file is copied to the ram disk during boot and the COMSPEC environment variable is set to the new location on the ram disk. This way the boot disk can be removed without the need to reinsert it after a big application has been stopped. The command line interpreter will be reloaded from the ram disk instead of the boot disk.

References

External links

Creating a customized Command Prompt shortcut
- Example of COMSPEC usage Windows administration DOS environment variables Windows environment variables {{windows-stub