TAL Programmer's Guide

Process Environment
Introducing the Environment
4–4 096254 Tandem Computers Incorporated
Extended Data Segments
Extended data segments provide indirect data storage in addition to storage in the
user data segment. References to extended data segments are not as fast as those to
the user data segment. An extended data segment can be as large as 127.5 megabytes.
When you declare arrays and structures by specifying the extended indirection symbol
(.EXT), the compiler automatically allocates and deallocates an appropriately sized
extended segment. The segment size is fixed during compilation, and the full segment
is allocated in one step. If you need a larger extended segment, use the LARGESTACK
directive (described in the TAL Reference Manual).
As shown in Figure 4-2, the automatic extended segment contains:
A global area—for global extended indirect arrays and structures
An extended stack—for local extended indirect arrays and structures
Figure 4-2. Automatic Extended Data Segment
Global extended indirect
arrays and structures
Local extended indirect
arrays and structures of
main procedure
Local extended indirect
arrays and structures of
current procedure
Available for dynamic
allocation by the TAL
compiler
Dummy stack marker
for main procedure
347
Global
area
Extended
stack
It is recommended that you use only the automatic extended data segment if possible.
If you must also allocate explicit extended data segments, follow the instructions in
Appendix B, “Managing Addressing.”