Programmer's key

The Programmer's key, or interrupt button, is a button or switch on a computer which causes an asynchronous interrupt request (IRQ) to be sent to the processor. If a debugger is installed on the machine, it is activated when the interrupt request is processed, allowing the user to view and usually modify the computer's internal memory. The interrupt is of highest priority, allowing debugging of interrupt handlers. This is quite useful in debugging software, which is why it gets its name.