Memory Allocation - AT&T 6300 Programmer's Manual

Advanced Features
MEMORY ALLOCATION
Memory space must be set aside for an
assembly language subroutine before it can be
loaded. To do so, use the 1M: option on the
GWBASIC command (refer to the GWBASIC
command in the Command Reference section).
The 1M: option sets the highest memory location
to be used by GWBASIC.
In addition to the GWBASIC code area,
GWBASIC uses up to 64K of memory
beginning at its data (DS) segment.
If extra stack space is needed when an
assembly language subroutine is called, you
can save the GWBASIC stack and set up a
new stack for use by the assembly language
subroutine. The GWBASIC stack must be
restored, however, before you return from the
subroutine.
The assembly language subroutine can be
loaded into memory in several ways, the most
simple being to use the BLOAD commmand (see
the BLOAD Command in the Reference
section). Also, you could execute a program
that exits but stays resident, and then run
GWBASIC. As a third choice, the assembled
instructions could be stored in DATA
statements and POKEd directly into memory.
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