Control Data Corporation 3300 Reference Manual page 277

MAGNETIC TAPE
GENERAL HEADER LABELS
All header label records are 80 characters (480 bits) long, and are unblocked. They are recorded
in even parity (BCD) at the same density as the remainder of the data file. Header records are
separated from succeeding data records by an interrecord gap only. Header label record fields
are defined below; they are positioned as shown within the physical record. Values that may be
used within these fields are also indicated.
Starting
Character Length in
Defined Values
Field Name Position Characters BCD Characters Only Function
Densityt 1 1 2, 5, 8
Specifies density
of recording file
Header Label 2 2
( ) Identifies record as
Identifier
header label record
Not used 4 2
Retention Code 6 3 000-999
Specifies, in days,
file retention period
File Namet 9 14
Any combination of Identifies file
legal BCD characters
Reel Number t 23
2
01-99
Sequence of reels
for multireel files
Date Written 25
6
Any legal numeric
Date written is used
date, expressed as with retention period
mmddyy
to determ ine release
date of file
Edition Number t
31
2 00-99 or blank
Identifies a single
file set
User Supplied
33 48 Any combination of
User comments field
Information
legal BCD characters
t Used by *DEF open unit function
E-6
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