HP 3000 Manuals HP 3000 Manuals
USER LABELS
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:
+------------+----------+-----------+-----------+------------+---------+
| | | | | #items/ | |
| version | length | #items | labels | label | size |
+------------+----------+-----------+-----------+------------+---------+
version is 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.