User's Manual

XEROX LASER PRINTING SYSTEMS TAPE FORMATS MANUAL 1-1
1. 1American National Standards
Institute (ANSI) labeled tapes
The American National Standards Institute has defined standard
labeled magnetic tapes in ANSI Standard X3.27—1969. The
structure of these tapes is described in the following sections on tape
marks and labels.
Tape marks
The tape mark is used on ANSI tapes in the following places:
• Following every file header label group
• Preceding and following the end-of-life label group (a double
tape mark follows the last, or only, file on tape)
• Preceding and following the end-of-volume label group (a
double tape mark follows the last volume).
Used in the manner described above, the tape mark identifies the
boundaries between the data and label groups of a file, and the label
groups in consecutive files.
Double tape mark A double tape mark (two consecutive tape marks) indicates that no
further data follows on the tape. A double tape mark also occurs
between a header label group and a trailer label group when a file
containing no information (a null file) is written. This null file double
tape mark is formed by the tape mark following the file header label
group and the one preceding the end-of-file label group.
Labels
There are two general classes of labels for ANSI tapes: operating
system labels and user labels. Operating system labels are
generated and processed by the operating system. User labels are
generated and processed by user programs.
Four types of labels Within these general classes, there are four types of labels, each 80
characters long. They are beginning-of-volume, beginning-of-file,
end-of-volume, and end-of-file. The names of the various classes
and types of labels are defined in table 1-1.
Note: In user labels, the letter ’a’ refers to any of the graphic
characters defined in ANSI Standard X3.4-1968.