Compatibility: 1.0+
Expects: AH    00H
CS    segment of Program Segment Prefix of terminating process
Returns: none
Info: Exits to the parent process; passes control to the Terminate
Vector in the PSP.  Identical to the INT 20H Terminate.  The CS
segment register must be set to the PSP.

Resets vectors for DOS interrupts 22H-24H (Terminate, Ctrl-Break,
and Critical Error) to values saved from the parent's PSP.
Flushes file buffers, but files should be closed if their length
has changed.

Notes:   It's easier and cleaner to use DOS fn 4cH (exit).

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DOS Fn 00H: Terminate a Program