User's Manual

UNIVAC SERIES 70 (US70) MAGNETIC TAPE ORGANIZATION
XEROX LASER PRINTING SYSTEMS TAPE FORMATS MANUAL 6-9
Data formats
Users may generate magnetic tape files composed of fixed length,
variable length, and undefined length records. The fixed and variable
length records may be collected further into fixed or variable length
blocks. All data blocks must contain 13 or more bytes.
US70 labeled and unlabeled tape formats
Listed below are the record formats that may appear on US70
labeled and unlabeled tapes.
Description Record lengths, blocked/unblocked
• Fixed length, unblocked
• Fixed length records, blocked (block lengths are variable, so
that the block length parameter is present)’
• Variable length, unblocked
• Variable length, blocked
• Undefined length, unblocked.
Note:
1. The US70 system does not create blocked, undefined record
format.
2. Block and record length values always include the block or
record length field (4 bytes each) in the count.
3. The record or block length is of binary format and is contained
in the first 2 bytes of the 4-byte field. For example, variable
length blocked records have the format shown in figure 6-10.
Alternate device tapes
The US70 operating system contains a facility for allocating devices
to files at execution time. One situation in which this might be used is
when a file that is generally printed on-line is written alternatively to
magnetic tape.
A file printed on-line may not generally contain printer cartridge
control information as a part of the file. Alternate device print tapes,
however, must contain carriage control characters. The programmer
is responsible for including them in each print line.
Tape organization
Alternate device tapes may be generated with standard labels, non-
standard labels, or no labels. Similarly, these tapes may contain fixed
or variable length records and may be blocked or unblocked.