What is an external / internal command?
Question
What is an external / internal command?
Answer
In MS-DOS there are two ways commands are executed. An Internal command, which is a command embedded into the command.com file, and an external command, which is not embedded into command.com and therefore requires a separate file to be used.
For example, if your computer does not have fdisk.exe and you try using the fdisk command, you would receive an error "Bad command or file name." Fdisk is an external command that will only work if fdisk.exe, or in some cases, fdisk.com, is present.
However, as long as MS-DOS is running on your computer internal commands such as the cd command will always be available and does not require any other files to run.
Computer Hope's MS-DOS page lists what commands are external and what are internal on each of the command pages. In addition, see the internal command page and external command page for a complete listing of each of the internal and external commands available.