← IGCSE Computer Science Paper 1

The nine functions of an operating system

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

Part of: IGCSE Computer Science 0478 — 4.1 Types of Software and Interrupts — Module 16

Understanding The nine functions of an operating system in IGCSE Computer Science Paper 1

What it does: The interface is a visible OS function because the user interacts with it directly. Memory management happens in the background and the user does not see it, but it is one of the nine OS functions. An OS manages memory (RAM) so that programs get the space they need. It does not write code for you. Multitasking shares CPU time between programs. Storing files is handled by the managing files function. Interrupts are signals that tell the CPU to stop and deal with an event. The OS handles them using interrupt service routines. Antivirus is utility software, not one of the nine core OS functions. Providing a platform for applications is a core OS function.

Common mistakes: An operating system has nine core functions, so the loop must run from 1 TO 9. Using 8 would miss one function. An IF statement in pseudocode needs the keyword THEN at the end of the condition line: IF job = "memory" THEN.

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Learning

Duo

Which of these is one of the nine core functions of an operating system?

Writing application source codeManaging memory

Matches

The OS has only one job: running the user interface

↓

Wrong because the OS has nine core functions, including files, memory, multitasking, security and user accounts, not just the interface.

Applying

Meanings

Term

OS functions

Meaning

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

Practice

1 Manage files

Testing

Gaps

os.manage()

Check Answer

Spots

1FOR n ← 1 TO 8

2 OUTPUT functions[n]

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Quick Questions

1. Which of these is one of the nine core functions of an operating system?

A. Managing memory ✓

B. Writing application source code

An OS manages memory (RAM) so that programs get the space they need. It does not write code for you.

2. Which function lets the user interact with the computer using windows, icons and menus?

A. Managing peripherals and drivers

B. Providing a user interface ✓

The user interface (such as a GUI) is a function the user sees directly. Peripheral management runs unseen in the background.

3. Which statement is correct?

A. The OS has nine core functions, and some run unseen in the background ✓

B. All nine OS functions are visible to the user on screen

Only a few functions, such as the interface, are seen by the user. Memory management, interrupt handling and multitasking mostly run unseen.

4. What is the purpose of the OS function 'managing multitasking'?

A. To store files permanently on the hard drive

B. To let several programs appear to run at the same time ✓

Multitasking shares CPU time between programs. Storing files is handled by the managing files function.

5. Which function checks that only users with the right permissions can open a file?

A. Providing system security and managing user accounts ✓

B. Managing memory

Accounts, passwords and permissions are security and user account jobs. Memory management decides where programs are placed in RAM.

Match the Pairs

Managing files → The OS creates, names, stores, moves, copies and deletes files and folders so data can be found again.

Handling interrupts → The OS responds to signals that ask the CPU to stop its current task, runs the matching routine, then lets the CPU carry on.

A function the user sees: the OS gives the user a way to control the computer with windows, icons and menus → Providing a user interface

A function that runs unseen: the OS shares RAM between programs so each has the space it needs → Managing memory

The OS has only one job: running the user interface → Wrong because the OS has nine core functions, including files, memory, multitasking, security and user accounts, not just the interface.

Managing peripherals means managing RAM → Wrong because managing peripherals and drivers deals with devices such as keyboards and printers, while managing memory deals with RAM.

Key Term

OS 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.

Fill in the Blanks

1. // Saves and organises data on disk os.manage(files)

Hint: Type the kind of item the OS stores on disk and organises into folders.

2. // Reacts when a device needs the CPU os.handle(interrupts)

Hint: Type the name of the signals that ask the CPU to pause its current task.

3. // Shares RAM between running programs os.manage(memory)

Hint: Type the resource the OS divides up between the programs that are open.

4. // Seen by user: GUI or CLI to control PC os.provide(interface)

Hint: Type the word for the part the user sees and uses to control the computer.

5. // Runs unseen: logins, passwords, rights os.manage(accounts)

Hint: Type the word for what each person has, with a login, password and permissions.

Spot the Error

Question 1

A FOR n ← 1 TO 8

B OUTPUT functions[n]

C NEXT n

Line A — An operating system has nine core functions, so the loop must run from 1 TO 9. Using 8 would miss one function.

Question 2

A job ← "memory"

B IF job = "memory"

C OUTPUT "Allocates RAM"

D ENDIF

Line B — An IF statement in pseudocode needs the keyword THEN at the end of the condition line: IF job = "memory" THEN.

Question 3

A job ← "security"

B purpose ← "draws windows"

C OUTPUT job & ": " & purpose

Line B — Providing system security means protecting data and the system, for example with passwords and permissions. Drawing windows belongs to the user interface function.

Question 4

A seen ← "user interface"

B unseen ← "managing memory"

C OUTPUT seen & " runs unseen"

Line C — The user interface is a function the user sees and uses directly. The functions that run unseen include managing memory and handling interrupts. The output should say it is seen.

Question 5

A device ← "printer"

B IF driver = TRUE THEN

C OUTPUT "Printer is ignored"

D ENDIF

Line C — When the correct device driver is installed, the OS can manage the peripheral and the printer works. The OS does not ignore it.

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