TAL Programmer's Guide

Process Environment
Introducing the Environment
4–2 096254 Tandem Computers Incorporated
Data Space The current data space of your process consists of:
A user data segment
An automatic extended data segment if needed
Any user-defined (explicit) extended data segments
(The term segment refers a nonextended segment except where the word extended is
specifically used.)
User Data Segment
The user data segment provides a private storage area for the variables of your
process. Your process can modify the content of the user data segment.
The system provides the user data segment automatically. This segment contains up
to 65,536 words, addressed consecutively from G[0] through G[65535]. (G represents
the global storage area.)
The lower half of the user data segment contains the global storage area and the data
stack. During the execution of your process, the system stores the process’ global data
in the global area. During activation of a procedure, the system stores the procedure’s
data in the local area of the data stack. During activation of a subprocedure, the
system stores the subprocedure’s data in the sublocal area of the data stack.
The upper half of the user data segment provides memory that you can allocate for
your data if you do not use the CRE. Appendix B, “Managing Addressing,” gives
information on using the upper half of the user data segment without the CRE.