IGCSE Computer Science 0478 — 4.1 Types of Software and Interrupts Hangman

The 60 key terms

1hardware

The physical parts of a digital system that you can touch, such as a keyboard, screen or CPU. Hardware needs software to tell it what to do.

2software

The set of instructions, or programs, that tells hardware what to do. You cannot touch it, and it needs hardware to run. Apps are one kind.

3system software

Software that provides the services the computer needs to run, such as the operating system and utility software, often working in the background without the user asking.

4application software

A program designed to help a user complete a specific task, such as browsing the web, writing a document or playing a game. It runs on top of the operating system.

6System software vs application software

System software runs the computer itself, e.g. the OS. Application software does jobs for the user, e.g. a word processor, and cannot run without system software.

7operating system

The software that manages a device's hardware and runs other software, like Windows, macOS, ChromeOS, Android or iOS. It handles files and memory and gives you the user interface.

8utility software

System software that helps maintain, look after and protect a computer, such as antivirus, backup and file compression. It is separate from the operating system.

9Antivirus software

A program that detects, blocks and removes malicious programs from a device.

10Firewall

A device or program that monitors and controls incoming and outgoing network traffic according to defined security rules.

11Backup system

A system that creates and retains separate copies of data so it can be recovered if the original is lost.

12defragmenter

A utility that rearranges the scattered pieces of files on a hard disk drive so each file is stored together, which speeds up reading. It is not needed for SSDs.

13disk formatter

Utility software that prepares a new drive or USB stick for use by creating a file system to store files in. It also erases any existing data on the device.

14compression utility

Utility software that makes files smaller to save storage space and send them faster, and can restore (unzip) them to their original form when needed.

15system vs application

Ask who the program serves: the computer itself (OS, antivirus, backup) is system software; a task the user wants done (word processor, game) is application software. Justify with 'because'.

16OS functions

The nine jobs of an OS: managing files, handling interrupts, user interface, peripherals and drivers, memory, multitasking, platform for apps, security and user accounts.

17file management

An OS function that keeps track of files and folders, lets users create, name, open, copy, move and delete them, and records where each file is stored.

18user interface

The part of a digital system that you see and use. You give input by touching, clicking or typing, and the screen shows you output.

19GUI

Graphical user interface: the user controls the computer with windows, icons, menus and a pointer instead of typing commands. It suits beginners but uses more system resources than a CLI.

20command-line interface (CLI)

A user interface where you type text commands to control the computer. It is precise and quick for experts, uses few resources, but is harder to learn because commands must be remembered.

21peripheral

An external device, wired or wireless, that connects to a digital system to add input, output or storage, such as a mouse, printer or USB drive.

22device driver

Software that lets the operating system talk to a piece of hardware, such as a printer, so the device works properly.

23peripheral management

The OS controls data passing to and from peripherals and loads the correct driver for each device so it can be used. Without a driver, the device does not work.

24RAM

Random Access Memory: fast, temporary memory that holds the data and programs currently in use. It is volatile, so everything in it is lost when the power is turned off.

25memory management

The OS decides which part of RAM each running program uses, keeps programs from overwriting each other's memory, and frees the space when a program closes.

26multitasking

The OS runs several programs at once by sharing CPU time in very short slices and switching quickly between them, so they appear to run together.

27platform

The OS provides a platform: a standard environment and shared services that apps ask for, so a program uses hardware through the OS instead of controlling it directly.

28system security

An OS function that protects the computer and its data from unauthorised access and attack using logins, access rights, updates and security tools.

29Operating system update

Installing the latest patches for the OS, fixing known security vulnerabilities and bugs.

30digital account

A personal record kept on a system, like a school, email, game or social account, that you must log in to reach. Each account holds your own information.

31permission

A rule that lets an account read, write or execute a file or resource. Read only views it, write can change or delete it, and execute runs it as a program.

32user account management

An OS function that creates, stores and controls user accounts, so each user logs in with a username and password and gets their own settings, files and access rights.

33scenario to function

Find what the OS is doing in a scenario, such as sharing the CPU, loading a driver or checking a password, then match it to one of its nine functions and explain with 'because'.

34firmware

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.

35ROM

Read only memory: non-volatile primary storage whose contents are fixed. It keeps the start-up (boot) instructions, so data stays when power is off. Also used in embedded devices.

36volatile memory

Memory that loses its contents when the power is off, like RAM. Non-volatile memory, like ROM and SSDs, keeps its data without power.

37bootloader

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.

38boot 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.

39software 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.

40application 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.

41CPU

The central processing unit is the 'brain' of a digital system. It carries out program instructions one after another and processes data. Its speed affects how fast tasks run.

42fetch-decode-execute cycle

The CPU repeats three stages for every instruction: fetch it from RAM, decode what it means, then execute it. The cycle then starts again with the next instruction.

43register

A very small, very fast storage location inside the CPU (not in RAM) that holds one item of data or one address, such as the PC, MAR, MDR, CIR or ACC.

44Program counter (PC)

A register in the CPU that holds the address of the next instruction to be fetched. It increments after each fetch and changes when the program jumps.

45interrupt

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.

47keyboard

An input device where pressing a key completes a circuit. The controller identifies the key and sends its character code to the computer, so text and commands can be entered.

48optical mouse

An input device with an LED or laser under it that lights the surface while a sensor takes rapid images to track movement and move the pointer. It has no ball.

49hardware 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.

50ZeroDivisionError

A Python runtime error raised when a number is divided by 0, or a remainder is taken with % 0. Guard against it with an if check or try/except.

51software 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.

52hardware 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).

53interrupt source

The origin of the signal. From a device, like a key press or mouse move, it is a hardware interrupt. From a running program, like divide by zero or a memory clash, it is a software interrupt.

54interrupt signal

A signal sent to the CPU by a device (hardware) or a running program (software) when an event, such as a key press, needs the CPU's attention.

55interrupt check

At the end of each fetch-decode-execute cycle the CPU checks for an interrupt signal. If none, it fetches the next instruction; if one, it switches to handling it first.

56interrupt priority

Each interrupt has a priority level. The CPU handles the most urgent one first, so a power failure can pause the handling of a less urgent key press.

57interrupt service routine (ISR)

A small program the CPU runs to deal with one particular interrupt. Each type of interrupt has its own ISR, kept in memory, and it is short so the CPU can quickly return to its task.

58save register contents

Before running the ISR, the CPU stores its register contents, including the program counter, so the interrupted task can later carry on exactly where it stopped.

59interrupt outcome

What the ISR does depends on the event: it reads a key press, updates the pointer, shows an error or stops a faulty program. Then the CPU resumes the task it was running.

60interrupt handling sequence

The ordered steps: an interrupt is generated, the CPU finishes its cycle and detects it, saves its state, runs the ISR, restores its state, then resumes the original task.

61OS interrupt handling

The OS receives each interrupt, picks the right ISR to run, manages priorities, then passes control back to the interrupted program so it can carry on.

62point and reason

A full-mark answer uses the correct terms (system software, firmware, bootloader, ISR), gives points in the right order, and adds a reason for each point.