An operating system (OS) is the main system software of a computer or phone. It sits between you and the hardware. It runs your programs, manages memory and devices, keeps files in order and gives you a screen to work with. Windows, Linux, Unix, macOS and Android are operating systems. Papers ask about OS functions and types, Windows features and settings, and a few DOS and Unix commands. This page covers them all.
42
Past questions on this page
Punjab Police SI & Constable
1985
Windows 1.0 released
By Microsoft
1991
Linux first released
By Linus Torvalds
1969
Unix begun
Bell Labs, USA
What an operating system is and does
The manager between you and the machine.
WHERE THE OS SITS
- UserYou give a command: click, tap or type.
- ApplicationsWord, a browser, a game.
- OSOperating systemManages the hardware and the applications.
- HardwareCPU, memory, disk, screen, printer.
| Function of the OS | What it means |
|---|---|
| Process management | Starts, runs and stops programs; decides which one gets the CPU |
| Memory management | Gives RAM to each program and takes it back |
| File management | Creates, saves, finds and deletes files and folders |
| Device management | Controls printers, keyboards, disks through device drivers |
| User interface and command interpretation | Gives you a screen (GUI) or a prompt (CLI) and acts on your commands |
| Security | Passwords and permissions: who may open which file |
KEY TERM
Device driver
A device driver is a small piece of system software that lets the OS talk to one piece of hardware, such as a printer or graphics card. Its purpose is to manage hardware resources.
OS→Driver→Printer
- Is it an OS? Linux, Windows, Unix: yes. Safari and Edge are web browsers and GIMP is an image editor: these are application software.
- Software that manages the computer hardware and user applications is the operating system, not a client, server or "web".
QUICK CHECK
An operating system can be defined as an interface between ______ and ______.
Tap an option to answer
Answer: C — user; hardware
Punjab Police SI, 2023. The standard definition is user and hardware. "Software; hardware" is the trap: the OS is itself software.
QUICK CHECK
Which of the following is NOT a function of an operating system?
Tap an option to answer
Answer: A — Execution of arithmetic operations
Punjab Police SI, 2021. Arithmetic is done in hardware by the ALU. The OS only manages memory, processes and commands.
QUICK CHECK
Which of the following is the purpose of a device driver in an operating system?
Tap an option to answer
Answer: A — To manage hardware resources
Punjab Police SI, 2023. A driver translates OS requests for one device. The interface, running apps and file permissions are other parts of the OS.
Types of operating system and a short history
Batch, time-sharing, real-time, multitasking, and the people behind Unix and Linux.
| Type | In simple words | Remember |
|---|---|---|
| Batch OS | Jobs are grouped and run one after another, with no user sitting at the machine | Second generation |
| Time-sharing OS | CPU time is split into small slices shared by many users | Third generation |
| Real-Time OS (RTOS) | Must respond within a strict, predictable time | Medical devices, machines, air-bags |
| Distributed OS | Many connected computers work together like one | Networks of machines |
| Multitasking | One user runs more than one program at a time | Music + browser together |
| Multiprocessing | Uses two or more processors (CPUs) at once | Linux supports it |
REMEMBER
Batch = 2nd, Time-sharing = 3rd: "B before T", just like in the alphabet.
Who made Unix and Linux
Ken Thompson and Dennis Ritchie
Creators of Unix at Bell Labs
- Began Unix at AT&T Bell Labs, USA, in 1969
- Dennis Ritchie also created the C programming language
Unknown author, Wikimedia Commons · Public domain
Linus Torvalds
Creator of the Linux kernel
- Released Linux in 1991 as free, open-source software
- Anyone may read, change and share its source code
Krd (photo), Von Sprat (crop), Wikimedia Commons · CC BY-SA 4.0
MILESTONES OF OPERATING SYSTEMS
- 1969Unix
Begun at Bell Labs by Thompson and Ritchie. Command-line first.
- 1975Microsoft founded
By Bill Gates and Paul Allen.
- 1981MS-DOS
Microsoft Disk Operating System: typed commands only.
- 1985Windows 1.0
Microsoft's first Windows: multitasking through a graphical user interface.
- 1991Linux
Linus Torvalds releases the Linux kernel.
- 2001Windows XP
Built mainly for keyboard and mouse.
- 2004Ubuntu
A popular desktop Linux, from Canonical.
- 2015Windows 10
The version most Windows questions in these papers are about.
- 2021Windows 11
The newer version. Some Settings paths look different from Windows 10, but the past questions on this page ask about Windows 10.
QUICK CHECK
Consider an embedded system designed for an important real-time medical device. Which type of software architecture would be most important to ensure predictable and timely responses to sensor inputs?
Tap an option to answer
Answer: A — Real-Time Operating System (RTOS)
Punjab Police Constable, 2025. "Predictable and timely" is the definition of a real-time OS. Batch and time-sharing systems give no fixed deadline.
QUICK CHECK
Which of the following combination is NOT correct? I. Batch operation system - Second generation. II. Time sharing operating system - Third generation.
Tap an option to answer
Answer: D — Neither I nor II
Punjab Police Constable, 2021. Both pairs are correct, so neither is "not correct". Read NOT questions twice.
Windows, Linux, Unix and mobile systems
Who makes which OS, and which ones run on desktops or phones.
| OS | Made by |
|---|---|
| Windows | Microsoft |
| macOS, iOS | Apple |
| Android, Chrome OS | |
| Bada | Samsung (its own mobile OS, used around 2010; later replaced by Tizen) |
| BlackBerry OS | BlackBerry (earlier called Research In Motion) |
| Symbian | Symbian Ltd, used mostly on Nokia phones |
| Ubuntu | Canonical (a Linux distribution) |
| Linux | Linus Torvalds and a worldwide open-source community |
KEY TERM
Open source
Open-source software publishes its source code. Anyone may read it, change it and share it. Linux is the best-known open-source OS. Windows and macOS are proprietary (owned and closed).
Source code→open to all→Linux
COMMON TRAPS
- Windows is the product; Microsoft is the company that made it.
- There is no "Dell OS". Dell makes computers and ships them with Windows or Linux.
- In 1985 Microsoft launched Windows. Unix is older (1969) and Linux is newer (1991).
QUICK CHECK
Which of the following is a proprietary operating system developed by Samsung for mobile phones?
Tap an option to answer
Answer: A — Bada
Punjab Police SI, 2023. Bada was Samsung's own mobile OS. BlackBerry OS, Symbian and MeeGo came from other companies.
QUICK CHECK
Which of the following statement is correct? I. Linux is an open-source operating system. II. Linux is a multitasking and multiprocessing operating system.
Tap an option to answer
Answer: A — Both I and II
Punjab Police SI, 2021. Linux's code is open to all, and it runs many programs on one or more processors. Both are true.
CLI and GUI, with DOS and Unix commands
Typing commands vs clicking icons, and the commands papers ask.
KEY TERM
GUI
The GUI lets users run programs and give instructions through icons, menus and other visual options. The mouse is only the hardware you point with; the GUI is the software you point at.
Icon→Click→Program opens
| Job | Windows / DOS | Unix / Linux |
|---|---|---|
| List files | DIR | ls |
| Make a new folder | MKDIR (or MD) | mkdir |
| Change folder | CD | cd |
| Copy a file | COPY | cp |
| Delete a file | DEL | rm |
| Rename or move a file | REN / MOVE | mv |
QUICK CHECK
Which of the following operating systems comes only with a command-line interface?
Tap an option to answer
Answer: B — MS-DOS
Punjab Police SI, 2023. MS-DOS has only a typed prompt. The others are GUI systems that also offer a terminal.
QUICK CHECK
Which of the following pair is correct regarding DOS commands? I. Internal command – Resides on disk II. External command – Resides always in memory
Tap an option to answer
Answer: D — Neither I nor II
Punjab Police SI, 2021. The two have been swapped. Internal commands stay in memory; external ones are files on disk.
QUICK CHECK
Which of the following command is used to rename a file in Unix?
Tap an option to answer
Answer: C — mv
Punjab Police SI, 2022. mv moves a file, and moving it to a new name renames it. cp copies, rm deletes, ls lists.
The Windows desktop: taskbar, Recycle Bin and File Explorer
What you see after Windows starts, and where things go.
THE WINDOWS 10 TASKBAR, LEFT TO RIGHT
- Start buttonFar left. Opens the Start menu.
- Search boxType to find apps and settings.
- Open programsA button for every program you have open now, plus pinned ones.
- system trayNotification areaFar right: clock, internet, battery %, volume icons.
First screen
Desktop
The first screen you see after Windows loads: wallpaper, icons and the taskbar.
Deleted files
Recycle Bin
Delete key or right-click → Delete sends a file here. You can restore it. Shift + Delete skips the bin.
When idle
Screen saver
A moving picture that appears when the computer is left idle for some time.
Always there
Wallpaper
The background picture of the desktop, shown all the time.
KEY TERM
Clipboard
When you select text and press Ctrl + C, the copy goes to the operating system's clipboard, a temporary store in memory. Ctrl + V pastes it, even into another program.
Ctrl + C→Clipboard→Ctrl + V
QUICK CHECK
In Windows OS, the area at the extreme right of the taskbar, which contains a clock and a group of icons, is called _______.
Tap an option to answer
Answer: B — Notification area
Punjab Police SI, 2023. The clock, network and battery icons sit in the notification area. The Start menu opens from the far left; the Ribbon is inside Office apps.
QUICK CHECK
In the Windows OS, when you delete an item from any of the drives on your computer by making use of the Delete key or even by simply right-clicking and selecting the ‘Delete’ option, the file is moved to ________.
Tap an option to answer
Answer: A — Recycle Bin
Punjab Police SI, 2023. A normal Delete only moves the file to the Recycle Bin, so it can be restored. Shift + Delete removes it for good.
QUICK CHECK
A moving picture that appears on a computer screen when the user does not use the computer for a while is:
Tap an option to answer
Answer: D — Screen Saver
Punjab Police SI, 2023. A screen saver starts after a set idle time. Wallpaper is the trap in similar questions: it is shown all the time.
Windows 10 settings and Control Panel paths
Mouse, date and time, display, printers and the version number.
| Task | Path in Windows 10 |
|---|---|
| Mouse settings (quick) | Start → Settings → Devices → Mouse |
| Mouse properties (classic) | Control Panel → Hardware and Sound → Devices and Printers → Mouse → Apply |
| Add or remove a printer | Control Panel → Hardware and Sound → Devices and Printers |
| Time and time zone | Start → Settings → Time & Language → Date & time |
| Change date and time (other ways) | Right-click the clock → Adjust date/time; or Control Panel → Clock, Language and Region → Date and Time |
| Display / appearance | Right-click the desktop → Personalize (or Display settings) |
| Windows Features | Control Panel → Programs → Programs and Features; or Settings → Apps → Apps and features → Optional features; or search "Windows Features" |
| Computer name, hardware, remote, protection | System Properties |
| See the Windows version | Win + R (Run) → type winver |
COMMON TRAPS
- The Settings app has no "Programs" section. "Programs and Features" is in Control Panel. Settings uses Apps.
- Mouse and printers are hardware: look under Devices (Settings) or Hardware and Sound (Control Panel).
- The label is Date & time, date first. "Day & Time" and "Time & Date" are made up.
- Right-clicking the clock gives date/time options, not display settings.
QUICK CHECK
Which of the following are the correct steps for changing mouse properties in Windows 10? (i) Go to ‘Control Panel’ from the Start menu. (ii) Click on ‘Mouse’ under Devices and Printers. (iii) Select ‘Hardware and Sound’. (iv) Change required mouse properties and ‘Apply’ changes.
Tap an option to answer
Answer: D — (i), (iii), (ii) and (iv)
Punjab Police SI, 2023. Order matters: Control Panel, then Hardware and Sound, then Mouse, then Apply. Option B lists all four in the wrong order.
QUICK CHECK
In the Run dialog box, which command is used to identify the Windows operating system version?
Tap an option to answer
Answer: C — winver
Punjab Police SI, 2023. winver (Windows version) opens the About Windows box. The other three are not Windows commands.
Quick revision
Full forms, traps and one-line facts.
FLASHCARDS
Tap to check
- OS
- Operating System
- MS-DOS
- Microsoft Disk Operating System
- GUI
- Graphical User Interface
- CLI
- Command Line Interface
- RTOS
- Real-Time Operating System
- Who made Windows?
- Microsoft (Windows 1.0, 1985)
- Who made Linux?
- Linus Torvalds (1991)
- Samsung's mobile OS
- Bada
- Rename a file in Unix
- mv
- New folder in Windows CMD
- MKDIR (MD)
- Windows version in Run
- winver
- Clock and battery icons
- Notification area
COMMON TRAPS
- The taskbar shows the programs you have open now, not every program ever installed or used.
- Screen saver = when idle. Wallpaper = always.
- The ALU does arithmetic and the compiler translates programs. Neither is an OS function.
- Batch = 2nd generation, time-sharing = 3rd generation.
Also asked onceTap to open
- Touch: desktop Windows XP was built for keyboard and mouse, without a touch interface. Windows 7 brought multi-touch gestures, and Windows 10 supports touch too.
- System Properties is the Windows section for the computer name, hardware settings, user profiles, system protection and remote (connectivity) settings.
- In File Explorer, the folder's location appears in the address bar near the top of the window.
- Ubuntu is an example of a desktop operating system (iOS, Symbian and Android are mobile).
- Multitasking = the ability to run more than one program at a time. (Overloading, reading and scanning are not.)
CHECK YOURSELF
You deleted an important file by pressing Delete. Where will you find it, and how is Shift + Delete different?
Show answer
It is in the Recycle Bin; open it, right-click the file and choose Restore. Shift + Delete skips the Recycle Bin and deletes the file permanently.