When you are using a Microsoft MS-DOS command prompt shell window you can type the following commands into the window.
The command interpreter for DOS runs when no application programs are running. When an application exits if the transient portion of the command interpreter in memory was overwritten DOS will reload it from disk. Some commands are internal—built into COMMAND.COM; others are external commands stored on disk. When the user types a line of text at the operating system command prompt COMMAND.COM will parse the line and attempt to match a command name to a built-in command or to the name of an executable program file or batch file on disk. If no match is found an error message is printed and the command prompt is refreshed.

External commands were too large to keep in the command processor or were less frequently used. Such utility programs would be stored on disk and loaded just like regular application programs but were distributed with the operating system. Copies of these utility command programs had to be on an accessible disk either on the current drive or on the command path set in the command interpreter.

In the list below commands that can accept more than one file name or a filename including wildcards (* and ?) are said to accept a filespec (file specification) parameter. Commands that can accept only a single file name are said to accept a filename parameter. Additionally command line switches or other parameter strings can be supplied on the command line. Spaces and symbols such as a "/" or a "-" may be used to allow the command processor to parse the command line into filenames file specifications and other options.

The command interpreter preserves the case of whatever parameters are passed to commands but the command names themselves and file names are case-insensitive.

Many commands are the same across many DOS systems but some differ in command syntax or name.