User's Manual

UNIVAC SDF TAPE FORMAT
11-4 XEROX LASER PRINTING SYSTEMS TAPE FORMATS MANUAL
Control records
This section provides information about control records.
Label control block The first of the control records, the label control block (type O‘50’) is
actually the first record of the file. The Xerox printer checks to see
that the tape is a print tape (O‘25’ for “P”). It also checks that the
length of the label control block is 6 or 9 Univac words or some other
length. If other than 6 or 9 Univac words in length, the label control
block is assumed to have the same initial structure as the 9 Univac
word record. This provides for processing of label control blocks of
20 Univac words in length as well as other nonstandard lengths that
might be produced by given sites. The label control block is
described in table 11-4.
Processing of other control record
codes
Control record codes for continuation of previous data record (O‘51’),
end-of-reel (O‘54’), and end-of-file (O‘77’) are also processed.
Continuation records are discussed in the “Data records” section.
End-of-file or end-of-volume processing is initiated upon recognition
of control image records with code O‘77’ or O‘54’. In either case, the
rest of the current input block is truncated.
Translation mode change control records (type O‘42’) indicate a
character representation change from Fieldata to ASCII (or vice
versa) and are also processed.