IGCSE Computer Science Paper 1 Definitions Worksheet: 4.1 Types of Software and Interrupts (Modules 390–408)
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Key terms
Write what each term means, in your own words.
1
firmware
2
bootloader
3
boot sequence
4
software stack
5
application dependency
6
interrupt
7
hardware interrupt
8
software interrupt
9
hardware interrupt vs software interrupt
Answer Key
IGCSE Computer Science Paper 1 · Modules 390–408 · Student wording will vary for definitions
1firmware — Permanent software stored in a chip on the hardware. It gives the hardware its basic instructions and is kept when the power is off. Found in routers and PCs.
2bootloader — A small program stored in firmware that runs first at power-on, finds the operating system on storage, copies it into RAM and hands control to it.
3boot sequence — Power on, the bootloader in firmware runs and loads the OS from storage into RAM (which is empty at power-on). Once the OS is ready, the user can open applications.
4software stack — The layers of a computer: applications run on the operating system, which runs on firmware, which runs on hardware. Each layer depends on the layer below it.
5application dependency — An application cannot run on its own: it needs the OS to manage resources, the firmware to start the OS and the hardware to carry out its instructions.
6interrupt — A signal sent to the CPU telling it to pause its current task so something more urgent can be dealt with. The CPU then returns to the original task. It is not a crash.
7hardware interrupt — A signal sent by a hardware device, such as a keyboard, mouse or printer, to tell the CPU it needs attention, for example a key press or a printer out of paper.
8software interrupt — A signal sent to the CPU by a program or the processor itself when a process hits an error (e.g. divide by zero, invalid instruction) or needs an OS service, so the CPU pauses it.
9hardware interrupt vs software interrupt — A hardware interrupt comes from a device outside the program (key press, mouse move); a software interrupt comes from the running program itself (divide by zero, memory conflict).