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
code.

- -

DOS Fn 01H: Keyboard Input