Operating System, Application and Utility Software
Senior 3 · ICT
Operating System, Application and Utility Software
Lesson 1 of 5
22 min
Before Ishimwe reaches school, several operating systems have already worked for her. Her phone alarm runs on Android. The cash machine where her mother draws money runs an operating system built into the machine. In the computer lab she logs on to a Windows PC, and her files are kept on the lab server, whose operating system looks after forty computers at once. Others, inside the family's television and Wi-Fi router, she never sees at all. Each was built for a different job. In S1 you met the operating system as one kind of system software; this lesson sorts operating systems into types and shows you how to find out exactly which one a computer runs.
Definition
Operating system (OS): the system software that manages a computer's hardware and software resources, provides the services that application programs need, and gives the user a way to control the computer. Example: Windows 11 on a laptop; Android on a phone.
User interface: the part of the operating system that the user sees and works with to give instructions and receive results.
Booting: starting a computer. A small start-up program stored in the firmware (BIOS or UEFI) checks the hardware, then loads the operating system from storage into main memory (RAM). Switching on from off is a cold boot; restarting a computer that is already on is a warm boot.
Application programs never drive the hardware directly. A word processor that wants to save a file asks the operating system, and the operating system tells the disk what to do. The operating system is the layer between the programs you use and the machine underneath.
Figure 1. The layers of a computer system. Requests pass down through the operating system to the hardware, and results come back up.
| Interface | How you give instructions | Examples | Strengths | Weaknesses |
|---|---|---|---|---|
| Command line (CLI) | Type text commands at a prompt and press Enter | MS-DOS; Command Prompt and PowerShell in Windows; the Linux terminal | Fast for experts; needs little memory; commands can be saved in a script and repeated | Commands must be learned and typed exactly; one spelling mistake gives an error |
| Graphical (GUI) | Point and click on windows, icons and menus with a mouse or touchpad | Windows, macOS, the Ubuntu desktop | Easy to learn: you recognise a picture instead of remembering a command | Needs more memory and processing power; repeating a job many times is slow |
| Touch screen | Tap, swipe and pinch with your fingers | Android, iOS, iPadOS | Natural on phones and tablets; no mouse or keyboard needed | Small targets; typing long text is slow |
| Voice | Speak a command | Voice assistants in Android, iOS and Windows | Hands-free; helps users who cannot see the screen or use their hands | Struggles with noise and accents; a microphone that listens raises privacy questions |
Figure 2. Mock-up: the same folder in a command-line window and in a graphical window. On the left the user typed dir; on the right she simply opened the folder.
Definition
Command-line interface (CLI): a user interface in which the user types commands, one line at a time, at a prompt such as C:\>.
Graphical user interface (GUI): a user interface built from windows, icons, menus and a pointer (WIMP), which the user controls mainly with a mouse or by touch.
| Type | What it means | Example |
|---|---|---|
| Single-user, single-task | One user can run only one program at a time. | MS-DOS; the simple system inside a digital watch or a basic calculator |
| Single-user, multitasking | One user runs several programs at the same time and switches between them. | Windows 11 on a laptop with a browser, a music player and a word processor open together |
| Multi-user | Many users share one computer's processor, memory and storage at the same time, each with their own account and files, and the OS keeps them apart. | A Linux or Windows Server computer that many people use at once over the network |
An OS that can use two or more processors (or processor cores) at the same time is also called a multiprocessing operating system. Most modern desktop and phone systems are multiprocessing.
| Type | How it works | Where it is used |
|---|---|---|
| Batch | Similar jobs are collected into a group (a batch) and run together later, with no user interacting while they run. | Calculating every worker's salary at the end of the month; printing all report cards overnight |
| Time-sharing | The processor's time is cut into very short slices, given to each user or program in turn. The turns are so quick that every user seems to have the computer to themselves. | A server shared by many users; any multitasking computer |
| Real-time (RTOS) | Responds to input within a fixed, guaranteed time, every time. Being predictable matters more than being fast on average. | A car's airbag controller, a heart pacemaker, a factory robot, a drone's flight controller |
| Network | Runs on a server and manages user accounts, shared folders, printers and security for the computers on a network. | Windows Server or Ubuntu Server in a school lab or an office |
| Distributed | Spreads one job over many networked computers, which appear to the user as one system. | A search engine answering a search with thousands of servers at once |
Definition
Real-time operating system (RTOS): an operating system that guarantees to respond to an input within a fixed, very short time limit. Example: the controller that inflates an airbag a few thousandths of a second after a crash is detected.
Embedded operating system: a small operating system built into a device that has one main job, usually stored in the device's own memory chip. Example: the software inside a cash machine, a smart TV or a Wi-Fi router.
| Device | Operating systems | What shapes the design |
|---|---|---|
| Desktop and laptop | Windows (Microsoft), macOS (Apple), Linux distributions such as Ubuntu | Many programs, large screens, keyboard and mouse |
| Mobile (phones and tablets) | Android (Google, built on Linux), iOS and iPadOS (Apple) | Touch, battery life, mobile data, apps from an app store |
| Server | Windows Server, Ubuntu Server, Red Hat Enterprise Linux | Many users, running day and night, security, sharing |
| Embedded | Built into cash machines, smart TVs, routers, cars, washing machines | One fixed job; small memory; often real-time |
Operating systems also differ in their licence, which you met in S1: Windows, macOS and iOS are proprietary, while Linux is open source, so anyone may read, change and share its code.
Figure 3. Summary: one operating system belongs to several types at once. Windows 11 on a laptop is a GUI, single-user multitasking, desktop operating system.
GCFLearnFree (LearnFree): Computer Basics: Understanding Operating Systems (about 2 minutes). Watch for the operating systems it names for computers and for phones, and check each one against the table "Types by device" above.
Tip
Exam hook: three questions sort any operating system. How do I talk to it? (CLI, GUI, touch, voice.) How many users and programs at once? (single-task, multitasking, multi-user.) How fast must it answer? (batch can wait; real-time cannot.) A full answer names one type from each question.
A. With the GUI (Windows 10 or 11)
B. With the command line
cmd and press Enter. The Command Prompt opens.ver and press Enter. The version number appears.systeminfo and press Enter. Wait a few seconds, then find the lines OS Name, OS Version and Total Physical Memory.exit and press Enter to close the window.Illustrative output from steps B2 and B3 on one school laptop; your numbers will differ. Notice that Windows 11 still reports itself as version 10.0: the build number tells you which Windows it is.
Warning
Do not judge Windows by "10.0". Both Windows 10 and Windows 11 report version 10.0 at the command line. A build number of 22000 or higher means Windows 11; Windows 10 builds are lower. On a phone, look instead in Settings → About phone (the exact menu name varies by brand) for the Android version.
Worked example 1: name the types
Classify each system in two ways.
| System | Types | Reason |
|---|---|---|
| The controller that inflates a car's airbag | Embedded; real-time | It is built into the car for one job, and it must react within milliseconds every time. |
| The school server that stores every student's files and decides who may open them | Network; multi-user | It manages accounts and shared folders for many users on the network at once. |
| Windows 11 on a laptop with a browser, a music player and a word processor open | GUI; single-user multitasking | One person uses windows and icons and runs several programs at the same time. |
| The program that calculates all salaries at the end of the month | Batch processing | All the jobs are collected and run together, with nobody interacting. |
Worked example 2: CLI or GUI for a repeated job?
Every week a technician must rename 500 photo files on each of 30 lab computers. Which interface should he use?
Answer: the CLI. Its strength is that typed commands can be saved and repeated, which suits a large, repeated job. The GUI is better for a beginner doing a task once.
Practice
Sources and credits
This lesson adapts CC BY-SA material and is shared under CC BY-SA 4.0.
C:\Users\Ishimwe>ver
Microsoft Windows [Version 10.0.26100.1742]
C:\Users\Ishimwe>systeminfo
...
OS Name: Microsoft Windows 11 Pro
OS Version: 10.0.26100 N/A Build 26100
System Type: x64-based PC
Total Physical Memory: 8,031 MB
...