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The pages on this site contain documentation for very old MS-DOS software, purely for historical purposes. If you're looking for up-to-date documentation, particularly for programming, you should not rely on the information found here, as it will be woefully out of date.

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─────C/C++ Language─────────────────────────────────────────────────────────
 
     When an interrupt handler is called by an INT instruction, the
     interrupt enable flag is cleared. This means that no further
     interrupts (including keyboard, time-of-day, and other crucial
     interrupts) are processed until your function returns. If your
     function needs to perform significant processing, you should use
     the enable function to set the interrupt flag so that other
     interrupts can be handled.
 
     Interrupt handlers are special cases of C functions, since they
     are potentially reentrant. When designing an interrupt-handling
     function in C, consider the following guidelines:
 
        ■ If your function does not use the enable function to set
          the interrupt flag, it is not reentrant: important
          interrupts may be ignored.
 
        ■ If your function does use the enable function to set the
          interrupt flag, another interrupt may take place. Make sure
          that your handler takes this into account.
                                    -♦-