Compatibility: 2.0+
Expects: AH    4cH
AL    exit code  to return to parent (or for ERRORLEVEL)
Returns: none  (not applicable)
Info: Returns control of a child process to its parent, setting an exit
code value that may be queried by DOS Fn 4dH.

Control is passed to the Terminate Address of PSP of the exiting
program.  Ctrl-Break and Critical Error handler vectors are
restored to the addresses from the parent's PSP.

Notes:   The ERRORLEVEL value (used in DOS batch files) can be used to
check the exit code of the most recent program.

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DOS Fn 4cH: Terminate Program