Operating System (OS) – SS1 Digital Technologies Lesson Note (First Term)

An Operating System (OS) is the software that manages the computer hardware and lets a person and other programs use the computer.

Behavioural objectives

By the end of the lesson, students should be able to:

1. Define an Operating System.
2. State the four main functions of an OS.
3. Describe the four types of Operating System.
4. Give examples of Operating Systems for personal computers and for mobile devices.

What is an Operating System (OS)?

An Operating System is the “middleman” software that allows a human to communicate with the computer hardware.

• When it starts: it begins working as soon as you press the power button and the computer boots.
• What it manages: the CPU, memory, files, security and connected devices.
• What it allows: other programs, such as a browser or a word processor, to run.
• Why it matters: without it, you would have to write complex codes just to move a mouse.
• Examples: Windows, macOS, Linux, Android and iOS.

The restaurant example

• Chefs: the hardware that does the work.
• Food: the data that is processed.
• Manager: the OS, which takes the order, tells the chefs what to cook and makes sure the food reaches the table.
• Without the manager: the restaurant would be in chaos, just as a computer is useless without an OS.

Where does the OS sit in a computer system?

The OS sits between the user and application programs on one side and the hardware on the other.

What are the main functions of an OS?

The four most important functions of an OS are process management, memory management, file management and security.

1. Process management: it decides which program gets the “attention” of the CPU, so music and a typed document can run together without a crash.
2. Memory management: it allocates space in the RAM, like a librarian deciding which book goes on which shelf.
3. File management: it keeps track of where photos, videos and documents are saved and organises them into folders.
4. Security: it protects your information, for example when you use a password or fingerprint to unlock your phone.

What other jobs does an OS do?

• Device management: it controls devices such as the keyboard, printer and screen through programs called drivers.
• User interface: it gives the user a way to give commands, such as icons and menus on a screen.

What are the types of Operating Systems?

There are four types of Operating System: single-user single-tasking, single-user multi-tasking, multi-user and real-time.

Computers are used for different jobs, so we have different types of “Managers.”

1. Single-user, single-tasking OS

• Meaning: it allows one person to run only one program at a time.
• Example: MS-DOS, an early PC operating system.

2. Single-user, multi-tasking OS

• Meaning: it allows one person to run many programs at once, such as WhatsApp, Instagram and a web browser.
• Where used: most laptops and smartphones today.
• Examples: Windows, macOS, Android.

3. Multi-user OS

• Meaning: it allows many people to use the same computer at the same time through different terminals.
• Where used: big companies and servers that run websites.
• Examples: Linux, UNIX.

4. Real-Time OS (RTOS)

• Meaning: it is built for speed and precision, and must respond within a fixed, very short time.
• Where used: machines where a delay could be dangerous.
• Examples: air traffic control systems, robot arms in factories and the system that controls a car’s airbags.

How do the four types compare?

What are common examples of Operating Systems?

Common Operating Systems are grouped by the device they run on: personal computers and mobile devices.

Operating Systems for personal computers (PCs)

• Microsoft Windows: the most widely used PC system for work and school.
• macOS: used on Apple computers such as the MacBook.
• Linux: a free system often used by programmers and tech experts.

Operating Systems for mobile devices

• Android: used by Samsung, Tecno, Infinix and others, and developed by Google.
• iOS: used only on Apple iPhones.

Class activity

• Discussion: if your phone’s Operating System (Android or iOS) was deleted today, would you still be able to take a photo? Why or why not?

Evaluation

1. Define an Operating System in your own words.
2. List the four main functions of an OS.
3. What is the difference between a multi-tasking OS and a Real-Time OS?
4. Give two examples of a mobile operating system.
5. Which function of the OS is at work when a password unlocks a phone?

Assignment

Write a short note on any two types of Operating System. Give one example of each.