GDSX (Extended General Device Support) Manual

Design and Development
Extended General Device Support (GDSX) Manual—529931-001
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Space Usages and Limitations
scratchpad variables or user-defined attributes that are specific to a class of devices.)
To do this, you modify the USKELDEC file as desired and source in its templates
section at compile time.
If you are using either the USKELEX example program or the USKELEXC example
program for your user code, you source in the templates section of the ULHDECSE file
in the installed subvolume, which contains the standard LCB template and a modified
DCB template.
If you are using the USAMPLE example program for your user code, you source in the
templates section of the ULHDECS file in the installed subvolume, which contains the
standard LCB template and a DCB template modified for USAMPLE.
User code must source in the config^templates, config^data, common^data, and errors
sections from DCCBDECS. The config^templates section allows programmatic access
to the configuration parameters used by TSCODE. The config^data section contains
an allocation of the configuration template defined in the config^templates section.
(For a description of the variables defined see GDSX Configuration Parameters on
page 2-46.) Common^data contains some miscellaneous globals (including DCBTBL
and LINETBL) and DEFINEs. The errors section contains event mask definitions,
event result literals, and Guardian file error code literals.
From EXTDECS0, user code sources in the Guardian procedures that you intend to
use. PEXTGDS contains EXTERNAL declarations for all TSCODE procedures
callable from USCODE. All the pseudo procedures and the utility procedures are
declared in PEXTGDS.
If the GDSX application must access files of size greater than 4 GB, the user code
must source in DCCBDEC2.
PEXTGDS2 contains EXTERNAL declarations for all TSCODE2 procedures callable
from USCODE2. All the pseudo procedures and the utility procedures are declared in
PEXTGDS2.
Naming Conventions
When writing code, you are free to choose identifiers conforming to normal TAL rules.
If you use a local variable whose identifier starts with a circumflex character (^), be
sure that TSCODE does not use the identifier for a global variable.
Space Usages and Limitations
Because USCODE is bound with TSCODE to become a GDSX runnable unit, there are
limitations in code space and data space in user code. However, as multiple code
spaces are available, code space is not likely to be a problem.
Regarding the data space, GDSX uses a user data segment with a size of 64 pages.
TSCODE uses two extended segments—one for trace data (with trace^seg^id equal to
Caution. Although the DCB template is user-modifiable, the LCB template is not.