A computer system has a mouse. An interrupt is sent to the CPU every time a button on the mouse is clicked.

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2025). The mark or mark type is shown in brackets.

1. [1] Hardware (interrupt)
2. [4] Any four from: • Checks the priority of the interrupt • If priority is higher, it halts the current process • stores it on a stack • fetches the interrupt • checks the source of the interrupt • calls the interrupt service routine (ISR) / interrupt handler to process the interrupt • If priority is not higher, it continues with current process
3. [2] It is sent one bit at a time // It is sent down a single wire
4. [2] Any two from: • The mouse can be powered by the device • It is a universal connection • It is backward compatible • Less chance of skewing // Less chance of errors • Supports different data transmission speeds • Adequate transmission speeds • The cable cannot be inserted incorrectly • The device is automatically detected // Driver is automatically installed when device is connected
5. [1] Any one from: • Slower transmission than a parallel connection • Wire may get in the way // wire may limit movement of mouse