Unlike the DOS internal commands, which are loaded into primary memory (ram) along with COMMAND.COM at boot time, the DOS external commands are disk-bound. This means they
must be fetched from secondary memory (disk) and loaded into primary memory (ram) each time they are used.
FORMAT.EXE, CHKDSK.COM, and DISKCOPY.EXE are three examples of
external commands. Their syntax follows.
Prepares a diskette for use by DOS.
Syntax: FORMAT [d:]
Parameters: [d:] = Drive which is to receive the format.
- /s Include all system files necessary to make disk "bootable"
- /b Reserve space for system files on diskette. (Formats 320k instead
- /v Volume label of 11 characters
- To format a diskette in drive B: without system files:
- To format a diskette in drive A: with system files:
FORMAT A: /s
- To give the formatted diskette a volume name, include the /v
FORMAT A: /V
- Combine switches to format a boot diskette with a volume label:
FORMAT A: /S /V
Analyzes disk or diskette (first and only parameter) and displays disk and
memory status report.
Syntax: CHKDSK [d:] [/f] [/v]
Parameters: [d:] = Drive upon which to perform CHKDSK.
- /f Fix. Writes lost clusters to a disk file and corrects file
- /v Verbose. Lists all files on a disk.
- To display statistics about the diskette in drive A:
- To display statistics about the first hard disk and fix any lost
CHKDSK A: /f
Makes an exact copy of a diskette, including hidden system files if they
Syntax: DISKCOPY [d1:] [d2:]
Parameters:[d1:] = Drive for source diskette, [d2:] = Drive for target
- To make an exact copy of a diskette in drive A: to a diskette in B:
DISKCOPY A: B:
- To make an exact copy of a diskette using only drive A:
DISKCOPY A: A:
(Change source and target diskettes as requested).
DISKCOPY asks for a SOURCE diskette (the diskette being copied) and a
TARGET diskette (the diskette being copied to). The TARGET diskette need
not be formatted, DOS will format it while doing the DISKCOPY. If the
SOURCE diskette is bootable, the system will be transferred to the TARGET
as well. The two disk drives must always use the same media.