System software and interrupts — GCSE Computer Science practice questions

Question 1

A school's IT technician is setting up new laptops for a computer room. She installs several programs.

Which of these programs is **utility software**?

Accepted Answer

C: An anti-virus program. Utility software is system software that helps to maintain, protect or manage the computer, for example anti-virus, file compression or backup programs. An anti-virus program scans the laptop for malware and removes it. A web browser, a photo editor and a spreadsheet all let the user carry out a task, so they are application software.

Question 2

Malik's laptop is running a music player, a web browser and a video call at the same time. The operating system shares the processor's time between them, so they all appear to run at once.

Which function of the operating system is this?

Accepted Answer

B: Managing multitasking. Multitasking lets several programs appear to run at the same time. The operating system switches the processor between the programs very quickly and decides which one runs next, so each one gets a share of processor time. Managing files, peripherals and security are other OS functions.

Question 3

A processor checks its interrupt queue and finds an interrupt with a **higher** priority than the task it is running.

What does the processor do **before** it runs the interrupt service routine (ISR)?

Accepted Answer

A: It saves the current task, including the contents of its registers, so the task can be continued later. Because the interrupt has a higher priority, the processor stops the current task. It first saves the current task's state (the contents of its registers) and then runs the ISR. When the ISR has finished, the saved state is restored and the task continues where it stopped.