These commands are not permanent part of the memory. To execute or run these commands an external file is required. The external files used for the execution of external commands are EXE, COM, BAT.
The external commands are used for relatively complex jobs such as copying an entire diskette into another diskette to sort the disk to hide dehide the files and to optimize the memory space etc.
These files can be deleted copied and even renamed. Some commonly used external commands are DISK, COPY, FORMAT, DELTREE, ATTRIB, etc.