← IGCSE Computer Science Paper 1

OS function: providing a platform for running applications

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.

Part of: IGCSE Computer Science 0478 — 4.1 Types of Software and Interrupts — Module 27

Understanding OS function: providing a platform for running applications in IGCSE Computer Science Paper 1

What it does: The arrows show the order of the request. The app talks to the OS, and only the OS talks to the hardware. An app is built to use the services of one particular OS, so it needs that platform to run. Applications do not talk to hardware directly. They make a request to the OS, which uses the device driver to control the printer. The application requests a service from the OS. The OS manages the files and the storage hardware. Because the app asks the OS for services, the OS deals with the details of each different keyboard, screen or disk.

Common mistakes: An app must not control hardware directly. It should ask the OS for the service, so line 1 should be request OS.openFile("a.txt"). The app only requests printing. The OS sends the data to the printer through its driver, so the app does not send it directly.

Class: _____________________ · Name: _____________________ · Date: _________

Free printable worksheet with full answer key — or add this module to a class and your students practise it interactively.

🖨 Print worksheet + answer key Add OS function: providing a platform for running applications to a class →

This module's key terms are also in a printable crossword (Modules 373–389) and word search (Modules 356–389).

Take this worksheet further — free with Cloodit

Each concept is reinforced from every angle — learned, then applied, then tested.

Learning

Duo

Which statement describes how an application uses the printer?

It asks the operating system to print, and the OS controls the printerIt controls the printer hardware directly without the OS

Matches

Application -> hardware (no OS involved)

↓

Applications do not control hardware directly. The request must go through the OS: Application -> OS -> hardware.

Applying

Meanings

Term

platform

Meaning

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.

Practice

// The app asks the OS for services

Testing

Gaps

Application -> OS ->

Check Answer

Spots

1disk.openFile("a.txt")

2OS controls the disk drive

Cloodit turns curriculum-aligned coding content into journeys students work through one biome at a time.

Students earn collectable badges

Over 100 of them, across seven natural biomes.

Study Buddy

Students build a real study resource

Turns their work into revision material ready for Flash Cards and Exam study.

Diamond Dash — one of Cloodit's live, competitive Sprint games

Students lock in with Sprints

Live, competitive practice for the start of the lesson or a teacher-led lesson finisher.

A Cloodit certificate of achievement, ready to personalise and print

Custom printable certificates

Honour your top performers, or encourage a student who's trying hard — ready to print in seconds.

Add to class →

Quick Questions

1. Which statement describes how an application uses the printer?

A. It controls the printer hardware directly without the OS

B. It asks the operating system to print, and the OS controls the printer ✓

Applications do not talk to hardware directly. They make a request to the OS, which uses the device driver to control the printer.

2. What does it mean when the OS provides a 'platform' for applications?

A. It gives apps a standard environment and shared services to run on ✓

B. It turns every app into part of the hardware

A platform is the standard environment and set of services (such as file access and memory) that apps can ask the OS for.

3. A word processor needs to save a file. What does it do?

A. It sends a request to the OS to save the file ✓

B. It writes straight to the storage device's circuits

The application requests a service from the OS. The OS manages the files and the storage hardware.

4. Why can the same app run on computers with different hardware?

A. The OS handles the hardware differences, so the app only deals with the OS ✓

B. The app contains code for every possible hardware device

Because the app asks the OS for services, the OS deals with the details of each different keyboard, screen or disk.

5. A game is written for Windows. What is likely to happen if you try to install it on macOS?

A. It will always run, because all operating systems work the same way

B. It may not run, because it was written for a specific operating system ✓

Applications are written for the services and rules of a particular OS. A different OS may offer them differently, so the app may not work.

Match the Pairs

platform → The standard environment and shared services the OS provides so applications can run without controlling hardware themselves

app asks OS to save file → The application requests a service from the OS, which then uses the storage hardware on its behalf

An application does not control hardware directly: it sends a request to the OS and the OS uses the hardware → app -> OS -> hardware

Applications written for a specific operating system will only run on that OS, for example a Windows app on Windows → app_for_Windows.exe runs on Windows

Application -> hardware (no OS involved) → Applications do not control hardware directly. The request must go through the OS: Application -> OS -> hardware.

Each app needs its own code for every brand of printer → The OS gives a standard environment, so one app can run on different hardware. The OS and its drivers deal with the printer differences.

Key Term

platform

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.

Fill in the Blanks

1. Application -> OS -> Hardware

Hint: Type the word for the physical parts of the computer that sit at the end of the chain, reached only through the OS.

2. document = "report.docx" OS.Print(document)

Hint: Type the short name of the system software that the app asks to use the printer for it.

3. app.requires = "Windows" IF OS.name = app.requires THEN RUN app

Hint: Type the comparison operator that checks the installed OS matches the one the app was written for.

4. app.directAccess = FALSE app.requestVia = OS

Hint: Type the Boolean value showing that apps are not allowed to control the hardware directly.

5. app = "Browser" hardware = "tablet" OS.Run(app, hardware)

Hint: Type the variable name holding the program the OS runs, so the same app works on different hardware.

Spot the Error

Question 1

A disk.openFile("a.txt")

B OS controls the disk drive

C OS returns data to the app

Line A — An app must not control hardware directly. It should ask the OS for the service, so line 1 should be request OS.openFile("a.txt").

Question 2

A app <- WordProcessor

B request OS.print(doc)

C app sends data to the printer

Line C — The app only requests printing. The OS sends the data to the printer through its driver, so the app does not send it directly.

Question 3

A PC1 <- Windows, 8GB RAM

B PC2 <- macOS, 16GB RAM

C app runs on PC1 and PC2

Line B — The same OS gives the app the same platform on different hardware. With a different OS, the Windows app would not run, so PC2 should be Windows.

Question 4

A IF appOS <> userOS THEN

B RUN app

C ELSE

D OUTPUT "Not compatible"

E ENDIF

Line A — An app written for one OS runs only when the user's OS matches. The test should be appOS = userOS, not <>.

Question 5

A request OS.allocateMemory(5)

B request OS.readKeyboard()

C GPU.drawWindow(app)

Line C — The app must not call the graphics hardware directly. It should ask the OS: request OS.drawWindow(app).

Student with a class code? Join your class →