There are two types of user labels which both contain
descriptive information. One type contains global information
about the file and the data it contains. The other type contains specific
information about each item in the data set entry or compound data set
entry in the file. Each user label is 128 words in length and is placed in the file as follows:
----------------------------------------
| reserved for existing labels | 0-9
----------------------------------------
| last item description label | 10
----------------------------------------
| item description label | 11
----------------------------------------
| item description label | 12
----------------------------------------
| first item description label | 13
----------------------------------------
| global information label | 14
----------------------------------------
| data |
| |
----------------------------------------
|
Labels are in "reverse" order in the file. That is the last label
is the global information label, the second to last label is the
first item description label. An item description label contains
one or more item descriptions and there must be at least one item
description label.
When the file is built, space is reserved for pre-existing user
labels. Pre-existing labels may have been placed in the file
by an application program. If another application program
converts an existing file with user labels into an SD file,
the existing labels are not overwritten unless there are more
than ten. Pre-existing user labels begin at label 0.
As a result, the last item description label always occupies
label 10 in the SD file.
Global Information Label Format |
 |
The information in the global information label resides in the
following order:
| version | length | #items | #labels | #items/labels | size |
- version
is the the version of the SD Intrinsics that created the file.
The standard HP version format is followed (AA.NN.NN).
(8 characters, right justified)
- length
is the length of the records in bytes. This corresponds to the
size of the IMAGE entry. (integer)
- #items
is the number of items in each file record. This corresponds
to the number of items in the IMAGE entry. (integer)
- #labels
is the number of item description user labels. (integer)
- #items/labels
is the number of item descriptions that fit into one item
description label. Each label can hold INTEGER (128/size).
(integer)
- size
is the size of one item description in words. (integer)
Item Description Label Format |
|
The information in the item description label resides in the
following order:
| item | item | item | item | reserved | |
| name | type | offset | length | space | |
- item name
is the name of the item. (16 characters, left justified)
- item type
is one of the following codes indicating the type of item.
(integer)
1 = ASCII (type U and X)
2 = ASCII numeric in free form
3 = signed integer (type I)
4 = floating point real (type R)
5 = packed decimal (type P)
6 = COBOL computational (type J)
7 = unsigned integers (type K)
8 = zoned decimal (type Z)
9 = unused
10 = IMAGE compound item
The item types in parentheses correspond to IMAGE data types.
Note: Type 2 refers to ASCII representations of numbers
in free format. This includes 20, 45.7, 1.002E-10, -201.45.
- item offset
is the offset of the item in the file record in bytes.
This offset is relative
to the beginning of the beginning of a record where the first byte has
an offset of zero, the second has an offset of one, and so on. (integer)
- item length
is the length of the item in bytes. This distinguishes the long
and short forms of integers and reals. (integer)
- reserved space
is reserved for future enhancements to SD files. Four
words are reserved.
