Using DOS Commands with MS-DOS 6.22
Understanding DOS Commands
When you want your computer to perform an action, you communicate this request for service by entering commands at the DOS prompt. All DOS commands begin with a word, sometimes called a keyword, that identifies the action you want to take. Most DOS commands can accept parameters that refine the scope of the command. The DIR command, for example, tells DOS to show you a list of files written on a disk. Adding parameters to this command enables you to specify exactly the files you want listed.
Internal Versus External
DOS recognizes and responds to more than 80 commands. The programming to provide the most commonly used commands is contained within the DOS command interpreter, COMMAND.COM. You use commands such as DIR and COPY so frequently that making them available on demand whenever the computer is displaying a DOS prompt saves time. Because DOS does not have to launch (start) any program to provide the service, the commands provided by COMMAND.COM are called internal commands. You can tell which commands are internal by looking in the directory where DOS is installed. You never find COPY.COM or COPY.EXE, so you know that the COPY command is internal.
Other commands are stored as utility programs in a directory on your hard disk. Because these commands are not built into the command processor, they are called external commands. When you type a command that COMMAND.COM does not recognize as one of its internal commands, COMMAND.COM responds by looking on disk for a program file having the same name as the command. The FORMAT command, for example, is provided by programming found in the file FORMAT.COM, which is located in the DOS directory.
Whether internal or external, all DOS commands conform to rules that provide a grammar or syntax that is consistent throughout DOS. As a user, you need to make sure only that DOS can find the program files for external commands.