What is the difference Internal and External command?
Internal commands are functions that are built into the command interpreter, External commands are those not included in the interpreter, and are instead invoked by calling an external binary. Whether or not a particular command is internal or external varies by system. For example, echo is an internal command in MS-DOS (it is built into COMMAND.COM), while in most Linux systems, it is an external one, provided by GNU coreutils.DOS Internal command is associated with his Shell file Command.Com.. DOS external command is saved on the disk..