User's Manual

UNIVAC SERIES 70 (US70) MAGNETIC TAPE ORGANIZATION
6-8 XEROX LASER PRINTING SYSTEMS TAPE FORMATS MANUAL
Tape marks
This section describes labeled and unlabeled tape marks.
Labeled tapes
A tape mark follows every header label group and precedes and
follows every trailer label group. Two tape marks following a trailer
label group indicate the end of data on a volume. Figure 6-8 shows
an example of tape mark placement for standard labeled tapes.
Figure 6-8. Tape mark placement: Tapes with standard labels,
additional labels, and user labels
Null files It is possible, however, for two consecutive tape marks to appear on
tape and not signify the end of useful data on the volume. This
condition (null file) occurs when the end-of-volume and end-of-file
coincide (see figure 6-9).
Figure 6-9. Tape mark placement: Null files
Note: The notation (A) indicates the labels are part of File A.
Unlabeled tapes
Tapes using no labels optionally may begin with a single tape mark.
Files on these tapes normally are separated by tape marks. Two
adjacent tape marks signify the end of data on the tape (see figure 6-
7).