Compatibility: 1.0+
Expects: AH    01H
Returns: AL    character fetched from the Standard Input
Info: Reads (waits for) a character from the Standard Input Device.
Echoes that character to the Standard Output Device.  If
Ctrl-Break is detected, INT 23H is executed.

Notes:   Extended ASCII keystrokes (i.e., F1-F12, PgUp, cursor, etc)
will require two calls to this function.  The first call will
return AL=0.  The second will return AL with the extended ASCII

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DOS Fn 01H: Keyboard Input