Compatibility: 1.0+
Expects: AH    0cH
AL    DOS input function number (01H, 06H, 07H, 08H, or 0aH)
Returns: none
Info: Clears the Standard Input type-ahead buffer then invokes the DOS
input function specified by AL.  This forces the system to wait
for a character to be typed.

These values are allowed for AL:  01H  Kybd Input
06H  Console I/O
07H  NoEcho Unfiltered Input
08H  NoEcho Input
0aH  Buffered Input

Notes:   This is normally used in cases when you want to ignore any
keystrokes in the type-ahead buffer; for instance when
prompting for an OK before formatting a disk.

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DOS Fn 0cH: Clear & Input