What is an external and internal command?

What is an external and internal command?

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.