Tandy 1000 Basic Reference Manual page 364

Chapter 11 I Technical Information
Be careful when altering any files opened by the BASIC par-
ent program. The BASIC parent program should close all files
before executing SHELL and then reopen them upon return.
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When the SHELL command executes, BASIC tries t o free
any memory not being used. However, BASIC does not free
memory preserved with the
/M
switch. This may cause an
"Out of memory" error.
To
avoid this, load your machine language routines before en-
tering BASIC. Use Interrupt 27 to let the routines to exit
MS-DOS
but still remain in memory.
For more information, see the
Programmer's Reference
man-
ual for your computer.
It
is available through your Radio
Shack Computer Center.
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Never use Interrupt 27 on a child process. If you attempt to
terminate a child process but have it remain in memory,
BASIC may not have enough room to expand its workspace to
its original size. If the workspace cannot be restored, BASIC
closes all files, prints the error message "SHELL can't con-
tinue," and exits to
MS-DOS.
You cannot run BASIC as a child process to itself.
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