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File No. GENL 20
Systems Reference Library
IBM Standard Tape Label
This publication describes the format of the IBM
standard tape label and the conventions for its use.
The publication for any program that implements the
standard label will indicate that the program does so.
The standard label was designed for use on tapes for
the following tape units:
1. IBM 729 II, III, IV, V, and VI Magnetic Tape Units
2. IBM 7330 Magnetic Tape Units
3. IBM 7340 Hypertape Drives
The IBM standard tape label contains 120 alphameric
positions and serves as both a header label and a trailer
label. There are two types of trailer labels:
end-of-file (EOF) trailer labels and end-of-reel (EOR)
iJ 19F3. by Internati~nal Business Machines Corporation
Copies of this and other IBM publications can be obtained through IBM Branch
Offices. Address comments concerning the contents of this publication to
Programming Systems Publications, IBM Corporation, P. o. Box 390, Poughkeepsie, N. Y.
TAPE FORMATS AND LABELING RECORDING METHOD
Figure 1 illustrates the use of the standard label in All header and trailer labels must be written in
the basic tape data formats and on data tapes contain- binary coded decimal (even parity) regardless of the
ing physical tape records (blocks) of checkpoint data. recording method used for the data in the body of the
The various tape formats are described below. file.
A single-reel file is a single file contained on a single
reel of tape. The first block is the standard label; On 7340 tapes, both header and trailer labels must
this is followed by a tape mark. The data blocks come be written in the unpacked mode, regardless of the
next; the last data block is followed by a tape mark. mode in which the data records are written.
This tape mark is followed by an EOF trailer label
and then another tape mark.
Multi - File Reel NOTES ON STANDARD LABEL FORMAT
1. Decimal notation is to be used in all label fields
A multi-file reel is a single reel of tape containing
containing numerical data.
two or more files. Each of these files is identical
2. Positions 6, 36, and 41 of the standard label are
to a single-reel file.
not to be used. The user is not to assume that these
positions will remain blank at all times.
A multi-reel file is a single file contained on two or
STANDARD LABEL FORMAT
more reels of tape. Each reel of a multi-reel file
is identical in format to a single-reel file except that
all reels but the last one have EOR trailer labels.
Field 1: Label Identifier
The last reel of the file has an EOF trailer label
instead of aILEOR trailer label.
The contents of this field identify the type of label as
Checkpoint Blocks on Data Tapes
The manner in which checkpoint blocks are recorded
1HDRb Header label
on data tapes is specified in Field 19 of the standard
1EOFb End-of-file trailer label
1EORb End-of-reel trailer label
Additional codes will be assigned by IBM as required.
HEADER LABE LS
When a tape is entered into a system of labeled tapes,
Field 2: Retention Period
the new tape should have a header label followed by
a tape mark. The header label should contain
information in the Label Identifier and Reel Serial
Number fields only (see the format description The contents of this field indicate the number of days
below). (0001-9998) the file is to be retained after the
creation date. The field should contain 9999 for files
TRAILER LABE LS to which an expiration date is not applicable.
On 729 II, III, IV, V, and VI tapes and 7330 tapes,
only the Label Identifier and Block Count fields are Field 3: Creation Date
written in the trailer label. 7340 tapes contain the Positions: 11-15
above two fields in the trailer label and, in addition,
may contain any other trailer label fields because The contents of this field indicate the year and day
of the ability of the 7340 to read backward. of the year the file was created. The year (00-99)
No trailer label field on any tape, other than the occupies the first two positions of the field, and the
field entitled "For Optional Usage", is available to day of the year (001-366) occupies the last three
the user for additonal label information; this is true positions of the field (e. g. , January 31, 1962 would be
even if the fi~ld is not being used in the label. be entered as 62031).
Field 4: File Identification Field 10: Checksum Indicator
Positions: 16-25 Position: 46
The contents of this field are assigned by the user The contents of this field indicate the presence of
and are unique to the file; this field identifies the or absence of checksums.
entire file. Field 4 contains ten alphameric Code Meaning
characters, including blanks. -0-- Not applicable or no checksum
Field 5: File Serial Number 1-9 Will be assigned by IBM for
Positions: 26-30 various types of checksums
The contents of this field are identical to the contents
of Field 6 of the first or only reel of the file. This Field 11: Block Sequence Indicator
field contains five alphameric characters, including Position: 47
The contents of this field indicate the presence or
Field 6: Reel Serial Number absence of block sequencing.
Positions: 31-35 Code Meaning
-0- Not applicable or no block sequence
The contents of this field are assigned to the reel field used
when it enters the system. The field contains five 1-9 Will be assigned by IBM for various
alphameric characters, including blanks. The reel types of block sequence fields
serial number normally is also written on the
physical label of the reel for visual identification.
Field 12: Tape Checking/Interpreting Indicator
Field 7: Reel Sequence Number Position: 48
The contents of this field indicate how bits are written
This is a four-digit field whose contents (0001-9999) on the tape to provide a means of verifying and/or
indicate the order of the reel within a given file. interpreting the data read from the tape.
Code 7030 Others
Field 8: Reserve -1- Single odd parity without Binary
Positions: 42-44 Error Correction Code
2 Single even parity without BCD
This field is reserved for future use to indicate the Error Correction Code
file number in a multifile reel. This file number 3 Single odd parity with Not applicable
will be 1 in the label(s) associated with the first file Error Correction Code
on the reel, and will be increased by 1 for each
succeeding file on the reel.
Field 13: Tape Data Recording Technique Indicator
Field 9: Density Indicator Position: 49
The contents of this field indicate the maximum number
The contents of this field give the density of the file as of bits (not including check bits) that may be recorded
indicated by the programmed set density instruction. as a unit (byte) on the tape.
(Density does not refer to packed and unpacked data. ) Code Meaning
Code Meaning -6-- 729 or 7330
-0-- Not applicable 8 Hypertape
1 Low density IBM will provide additional codes as they are required.
2 High density
Field 14: Tape Data Processing Technique Indicator Code Meaning
Position: 50 2 Checkpoint blocks are interspersed
with data blocks.
The contents of this field indicate the number of bits 3 Checkpoint blocks are written as
(not including check bits) out of a byte that are to be consecutive blocks. No data blocks
treated as a unit in processing. The Hypertape codes are written.
are: 4-9 Will be assigned by IBM if required
Code Meaning to indicate additional ways of
4 Each unit of data consists of four recording checkpoint blocks.
bits (packed data).
6 Each unit of data consists of six Field 20: Block Count
bits (unpacked data). Positions: 67-72
Field 15: Creating System This field is used in trailer labels only. Its contents
Positions: 51-54 indicate the number of physical tape records (blocks)
in the file that are used to record data. The block
The contents of this field denote the system that count does not include header and trailer labels, tape
created the file, e. g., 7074. marks, segment marks, checkpoint records, or
Field 16: Record Format other records not containing file data.
Position: 55 Field 21: Reserve
The contents of this field indicate the record format
of the file. This field is reserved for future use by IBM.
Codes will be provided by IBM as they are required.
Field 22: For Disk Usage
Field 17: Record Length Positions: 75-79
This field is not to be used in tape labels.
For fixed-length records, the contents of this field
give the number of characters per logical data Field 23: Reserve
record; for variable-length records, the contents of Position: 80
this field give the number of characters in the largest
possible logical data record of the file. This field is reserved for future use by IBM.
Field 18: Blocking Factor/Size Field 24: For Disk Usage
Positions: 61-65 Positions: 81-85
For fixed-length records, the contents of this field This field is not to be used in tape labels.
indicate the number of logical data records within
each tape block; for variable-length records, the Field 25: Reserve
contents of this field indicate the number of Positions: 86-91
characters in the largest possible tape block record
of the file. This field is reserved for future use as a field
containing cycle information.
Field 19: Checkpoint Indicator
Position: 66 Field 26: Reserve
The contents of this field indicate (1) the presence
and type or (2) the absence of checkpoint blocks. This field is reserved for future use by IBM.
-0-- Not applicable or no checkpoint Field 27: For Optional Usage
block Positions: 101-120
1 Checkpoint blocks immediately
follow the tape mark that comes This field may, at the user's option, contain additional
after the header label. The check- label data.
point blocks are followed by a tape
mark and then the next data block.
ALPHABETIC LISTING OF LABEL FIELDS
The label positions occupied by each field are given
in parentheses following the field number.
Field Number & Field Number &
Field Name Label Positions Field Name Label PositionS';
Block Count 20 (67-72) Reel Serial Number 6 (31-35)
Block Sequence Indicator 11 (47) Reserve 8 (42-44)
Blocking Factor/Size 18 (61-65) Reserve 21 (73-74)
Checkpoint Indicator 19 (66) Reserve 23 (80)
Checksum Indicator 10 (46) Reserve