Function 3301h          Set Ctrl-C Check Flag

    Turns Ctrl-C check flag on or off.

        Entry   AX = 3301h
                DL = 0 | 1   Set BREAK flag off | on

        Return  Nothing

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    If the Ctrl-C (Ctrl-Break) flag is off, DOS checks for Ctrl-C
    keystrokes only while processing I/O functions 01h through 0Ch.
    If the flag is on, DOS checks for Ctrl-C while processing other
    system functions, such as disk operations.

    The Ctrl-C flag affects all programs. If a program changes the
    state of this flag, the state change remains in effect even after
    the program terminates.