mtdump dumps the record structure of a tape image file in SIMH, E11, TPC, or
P7B format.  mtdump is invoked by

	mtdump {-secp} file1 file2 file3...

where -s specifies SIMH format, -e E11 format, -c TPC format, and -p P7B
format.  The default is SIMH format.  Output is to stdout, unless redirected.

SIMH format is as follows:

	4 byte record length 1
	record 1
	repeat of 4 byte record length 1
	4 byte record length 2
	record 2
	repeat of 4 byte record length 2
	:
	4 bytes = 00000000 for end of file

and so on.  Records are padded to even byte length.

E11 format is similar to SIMH format, but odd length records are not padded
to even length.

TPC format is as follows:

	2 byte record length 1
	record 1
	2 byte record length 2
	record 2
	:
	2 bytes = 0000 for end of file

and so on.  Records are padded to even byte length.

P7B format is confined to 7 track tapes, as follows:

	start of record + first 6b character and parity
	:
	last character
	start of record + first 6b character and parity

and so on.  A P7B tape must have a dummy "last record" with a start of
record indicator.  A tape mark is indicated by a character of 317 (start
of record, character 17, wrong parity for odd parity, reserved character
for even parity).

mmdir is a variant of mtdump that dumps the directory structure of an
Interdata MMD (multimedia diagnostic) tape.  The tape must be in SMIH
format.
