Booting · Software types · OS services · User interfaces · Utilities · File systems — complete study notes.
BIOS → POST → MBR → Bootstrap → RAM → OS → GUI
📘 Introduction to Operating Systems
Hardware, firmware, software — and how the OS brings them all together at startup.
🔷 What is an Operating System?
A computer consists of hardware,
firmware, and
software.
The Operating System is the sole software that manages the whole computer system —
it provides instructions for installing and managing application software, and
manages all input, output, and computer memory.
HWHardware — any physical component with a definite shape: mouse, keyboard, display, hard disk, printer
FWFirmware — booting instructions stored in ROM; displays initial text on screen
SWSoftware — a set of instructions given to the computer to perform activities
key The OS provides a user interface after loading into RAM
key The OS manages all hardware, software, input, output & memory
key Application software cannot run without an Operating System
🚀 How a Computer Boots — Step by Step
This whole process of loading the OS into RAM is called booting.
1 User powers on → CPU activates the BIOS (Basic Input Output System)
2 First program: POST (Power On Self-Test) — uses CMOS memory to check all hardware
3 Reads MBR (Master Boot Record) in boot drive via firmware 'bootstrap loader'
4 Loads the Operating System from boot drive into RAM
5 OS takes control of the computer and displays a user interface
💡 Booting means loading an Operating System into RAM (main memory). The word comes from "bootstrapping" — pulling yourself up by your own bootstraps.
📊 Types of Software
SYSSystem Software
a Operating System — manages HW & SW
b Utility Software — disk tools, antivirus
c Language Translators — assembler, compiler, interpreter
APPApplication Software
eg Word processing, spreadsheets, database, games, browsers
🔗 Software Layers
👤 Human User
⇅
📱 Application Software
⇅
🖥️ Operating System
⇅
🔧 Other System Software
⇅
⚙️ Hardware
📦 System Software — Three Types
OS
Operating System
Manages hardware and software. Provides user interface. The bridge between hardware and user.
UTL
Utility Software
Manages and analyses computer software. Antivirus, disk formatting, disk defragmentation etc.
LNG
Language Translators
Converts high-level languages to machine code (0s and 1s). Examples: Assembler, Compiler, Interpreter.
🌐 Common Operating Systems — 5.1.4
WIN
Microsoft Windows
Proprietary (paid license). Most popular worldwide. Versions: XP, Vista, 7, 8, 10, 11. Also: Windows Mobile, Windows Server.
Developer: Microsoft Corporation
MAC
Apple Macintosh
Proprietary (paid license). Developed by Apple Inc. Can ONLY be installed on Apple hardware.
Developer: Apple Inc.
UBU
Ubuntu
Based on Linux. Free and Open Source Software (FOSS). Download free: ubuntu.com
Developer: Canonical Ltd.
AND
Android
Developed by Google. Mainly for mobile devices. Free and Open Source Software.
Developer: Google LLC
HAN
Hanthana Linux
Based on Linux. Free to download. Sri Lankan distribution. Download: hanthana.org
Developer: Hanthana Community
💡 Proprietary Software = users must pay for a license. |
Free and Open Source Software (FOSS) = free to use, modify and distribute.
🖥️ Types of Operating Systems
Operating systems are classified by their functionality — how many users and tasks they can handle.
1U
Single User
Serves one person at a time only.
Example: MS-DOS
MU
Multi-User
Multiple users connected simultaneously.
Example: Linux, Windows Server
MT
Multi-Tasking
Run multiple processes at the same time.
Example: Windows 7/8, Ubuntu, Mac
RT
Real Time
Gives output without observable delay.
Example: ATM machines, Calculators
1. Single User Operating System
The Operating System which provides service to one person at a time is called a Single User OS.
def Only one user can log in and use the system at any given time
eg MS-DOS (Microsoft Disk Operating System) — text-based, CLI only
use Used in early personal computers; simple tasks like word processing
2. Multi-User Operating System
Allows multiple users to use a system simultaneously.
Commonly used in Mainframe or Server computers.
def Several users can connect to one computer system at the same time
eg Linux, Windows Server
use School/university labs, corporate networks, mainframe computers
3. Multi-Tasking Operating System
Allows multiple processes to run at the same time.
A single user can run multiple operations simultaneously.
def Multiple tasks share the CPU in rapid succession — appears simultaneous
eg Windows 7, Windows 8, Ubuntu, Mac OS
use Browsing internet while playing music while printing a document
4. Real Time Operating System (RTOS)
Gives output in real time without observable delays.
Specifically designed for particular devices.
def Responds to inputs and produces results within a guaranteed time frame
eg ATM machines, Calculators, scientific instruments, small gadgets
use Medical devices, aircraft control systems, industrial automation
📊 Comparison Summary
Type
Users
Processes
Response
Examples
Single User
1 at a time
Limited
Normal
MS-DOS
Multi-User
Many simultaneously
Multiple
Normal
Linux, Windows Server
Multi-Tasking
1+ users
Many at once
Normal
Windows 7/8, Ubuntu, Mac
Real Time
Device-specific
Critical tasks
Instant
ATM, Calculator
⚙️ Services of an Operating System
The OS provides two main services: managing computer hardware and providing a user interface.
Service 1 — Hardware Management
i Process Management
ii Memory Management
iii Device Management
iv File Management
v Security Management
vi Network Management
Service 2 — User Interface
CLI Command Line Interface — text commands with exact syntax
GUI Graphical User Interface — windows, icons, menus, pointer
why Allows tasks without complex instructions
User Interface is covered in detail in the 🖱️ User Interface tab.
i. Process Management
A running computer program or part of a program is called a process.
All computer activities run as either a single process or multiple processes.
def A task is broken into small units called processes inside the computer
eg Printing a letter = many small processes (reading file, formatting, sending to printer…)
mgr Allocates CPU time, memory, and I/O devices to each process
ord Orders processes in sequence — prioritises which runs first
Real Example: Typing on the keyboard while a document is printing —
these appear simultaneous but run as two separate processes. Changes made
after clicking Print do not appear in the printout because those processes
are already locked in sequence.
ii. Memory Management
RAM (Random Access Memory) plays a major role during computer functioning.
Input data is stored in RAM before going to the CPU; processed data is stored in RAM before output.
role Allocates enough memory for each process
role Frees memory once a process ends
tech Uses both Primary Memory (RAM) and Secondary Memory efficiently
eg Once Print command sent → data in RAM is printed. Later changes are not printed.
RAM SPACE ALLOCATION
JOB 1 — Active
JOB 2 — Waiting
JOB 3 — Waiting
JOB 4 — Free space
iii. Device Management
The OS manages all peripheral devices. Device controllers control peripheral hardware;
device drivers control the software components.
drv A device driver must be installed for each new device
drv Without driver: full features unavailable (e.g. printer duplex)
PnP Plug and Play — drivers installed automatically on first connect
eg New printer → OS installs driver automatically; manually if needed
COMMON PERIPHERAL DEVICES
🖨️ Printer📷 Camera🎮 Gamepad🖱️ Mouse💾 USB Drive🎧 Headset
iv. File Management
Data is saved in files; files are kept in folders for methodical management.
The OS manages all files and folders. File management covers: file properties, operations, access, and file systems.
✓ Making new files and saving them at suitable places
thrt Unauthorised access — deletion or destruction of data
OS OS uses techniques to protect from threats (up to some extent)
3rd External (third party) software also needed: antivirus, firewall etc.
⚠️ The OS alone cannot control all external threats — third-party antivirus software provides additional protection.
vi. Network Management
Operating Systems support wired and wireless connectivity for devices in a network (computers, printers, scanners).
Enables remote access and data communication — even multimedia. Cloud Computing is a key example.
wrd Wired connectivity — Ethernet cables, LAN
wls Wireless connectivity — Wi-Fi, Bluetooth
rem Remote access — control one computer from another
cld Cloud Computing — data stored and accessed via the internet
🖱️ User Interfaces of Operating Systems
How users interact with the computer — Command Line (CLI) vs Graphical (GUI).
CLI
Command Line Interface
Text-based. User types commands at a prompt using exact syntax. Used in early OS. Still available in all modern OS.
Example: MS-DOS, Terminal, Command Prompt
GUI
Graphical User Interface
Graphics-based. Navigate with mouse or fingertips. Much easier to use. WIMP: Windows, Icons, Menus, Pointer.
Example: Windows, Mac OS, Ubuntu Desktop
1. Command Line Interface (CLI)
Used by all early Operating Systems. Has a prompt where commands are typed using a keyboard.
Correct syntax must be used — even a small error gives wrong results.
CLI TERMINAL WINDOW
Microsoft Windows [Version 10.0]
C:\Users\Student>dir
Volume in drive C has no label.
Directory of C:\Users\Student
C:\Users\Student>cd Documents
C:\Users\Student\Documents>█
compCommand Prompt — shows current location (e.g. C:\Users\)
compCommand — the instruction typed by the user
compOutput — result displayed on screen
compCursor — blinking indicator showing input position
eg dir — list files; cd — change directory; cls — clear screen
✓ ADVANTAGES
+ Uses less memory and processing power
+ Faster for advanced users who know commands
+ More precise control over system operations
✗ DISADVANTAGES
– Difficult for beginners — must memorise commands
– No visual feedback — errors are hard to spot
– Not user-friendly for everyday tasks
2. Graphical User Interface (GUI)
Almost all modern OS use graphics. Navigate with mouse or fingertips.
Uses WIMP — Windows, Icons, Menus, Pointer.
🪟
WINDOWS
Rectangular areas showing open applications
🖼️
ICONS
Small images representing files, folders, apps
📋
MENUS
Drop-down lists of available commands
🖱️
POINTER
Cursor controlled by mouse or fingertip
✓ ADVANTAGES
+ Easy to learn — intuitive, no commands to memorise
+ Visual feedback — see changes in real time
+ Suitable for all types of users including beginners
✗ DISADVANTAGES
– Uses more memory and processing resources
– Slower for advanced users compared to CLI
– Less control over system-level operations
📊 CLI vs GUI Comparison
Feature
CLI
GUI
Interface
Text / commands
Graphics / visuals
Input method
Keyboard only
Mouse, keyboard, touch
Learning curve
Steep — must memorise
Easy — intuitive
Speed (expert)
Faster
Slower
Memory use
Less
More
Examples
MS-DOS, Terminal
Windows, Mac OS, Ubuntu
🔧 Utility Programs of an Operating System
Built-in tools that maintain, protect, and optimise the computer system.
📦 Types of Utility Programs
1Backup Software — copies files and backs up hard drives
2Disk Scanner — checks for errors in hard drive
3Disk Defragmentation — rearranges fragmented data for efficiency
4File/Data Compression — compresses large files into smaller files
5Task Manager — shows processes, programs, and computer status
6Anti-Virus Software — identifies and eliminates malicious software
7Clipboard — temporary storage for cut/copy/paste operations
9Data Synchronisation — consistency between source and target storage
10Disk Partitioning — divides one drive into multiple logical drives
11Screensavers — blanks screen or shows patterns when not in use
12System Profilers — detailed info about installed software and hardware
13Network Utilities — analyse connectivity, check data transfer, log events
💡 In the past, utility programs had to be bought and installed separately. Today most required utilities come built-in with the Operating System.
Disk Partitioning
A hard drive is one physical drive, but it is normally divided into many
logical partitions.
This process of dividing one drive into multiple logical drives is called disk partitioning.
when At first-time hard disk configuration
when When a new hard disk is added or replaced
⚠️ Re-partitioning deletes ALL data — take backup first!
⚠️ Important: When an already-partitioned hard disk is partitioned again, all data in that hard disk will be deleted.
WHY PARTITION?
1 Save different types of data in different drives (Software in C: · Data in D:)
2 Install more than one OS (Windows + Ubuntu dual-boot)
3 Meet OS requirements (separate partition for OS installation)
Windows: Partitions named C:, D:, E: … · USB drives, DVDs also get a letter Linux: All drives and partitions appear as folders (Directories) — no C:, D: labels
Disk Formatting
After partitioning, each drive must be formatted before it can store data.
Formatting prepares the drive using a file system format.
def Preparing a storage device (HDD, SSD, USB, floppy) to store data
how Done using a file format (FAT32, NTFS, ext4 etc.) in the OS
USB Flash drives come pre-formatted — ready to use immediately
⚠️ Formatting DELETES all data in the drive — backup first!
seq Partition → Format → Install OS (first time setup order)
Before → After partitioning → After formatting
Defragmentation
When a file is broken into pieces and stored in different parts of the disk, this is called
fragmentation.
Defragmentation rearranges the fragmented data so the disk works more efficiently.
why Large files split across disk when no single large space is free
why Deleted file gaps filled with pieces of new files → fragmentation
eff Fragmented files take longer to read → slows the computer
fix Defragmentation rearranges pieces into contiguous blocks
tip If computer is slow, defragmentation may help (Windows)
BEFORE vs AFTER DEFRAG
Fragmented — scattered pieces
Defragmented — contiguous blocks
🐧 Linux note: Linux OS leaves space between files and can relocate files, so fragmentation rarely occurs. No defragmentation utility needed in Linux.
📁 File Systems — Drives, Folders & Files
How data is named, organised, stored and managed in a computer.
📄 File Names and Extensions
Every saved file has two parts: a file name and a
file extension, separated by a full-stop (.).
The OS identifies the file type using the extension. Extensions are hidden by default.
File Name Structure
document.docx
↑ File name↑ Separator↑ Extension
To show extensions in Windows: Start → Control Panel → Folder Options → View → uncheck "Hide extensions for known file types" → OK
COMMON FILE EXTENSIONS
Extension
File Type
.exe
Executable / Program
.docx
Microsoft Word Document
.xlsx
Microsoft Excel Spreadsheet
.pptx
Microsoft PowerPoint
.accdb
Microsoft Access Database
.jpg / .png
Image files
.mp3
Audio file
.pdf
Portable Document Format
.html
Web Page
.txt
Plain Text File
💾 Drives
A drive is a storage location. After partitioning, each partition is seen as a separate drive.
C: First hard drive partition — default in Windows. Also where OS is installed.
D: Second partition of hard disk, or DVD/CD-ROM drive
E: F: Additional partitions or optical drives
G:+ External devices — USB flash drives, SD cards etc.
🐧 Linux: all drives appear as folders (Directories), not letters
EXAMPLE: MY COMPUTER
💽 Local Disk (C:) — 83.1 GB
💽 New Volume (D:) — 117 GB
💽 New Volume (E:) — 97.6 GB
📀 DVD RW Drive (F:)
🔌 Removable Disk (K:) — USB
📂 Creating Folders and Managing Files
CREATING A FOLDER
1 Select the drive where the folder is to be created
2 File Menu → New → Folder (or right-click → New Folder)
3 Type a suitable folder name and press Enter
FILE PROPERTIES
how Right-click a file → Properties
info Type of file (e.g. JPEG image)
info Size of file (e.g. 9.47 KB)
info Location (e.g. D:\Chap 5)
info Created / Modified / Accessed date & time
🔄 File and Folder Operations
COPY Select file/folder → Edit→Copy (Ctrl+C) → go to destination → Edit→Paste (Ctrl+V)
CUT Select file/folder → Edit→Cut (Ctrl+X) → go to destination → Edit→Paste (Ctrl+V)
RENAME Select file/folder → File menu → Rename → type new name → Enter
DELETE Select file/folder → File menu → Delete (or Del key) → click Yes → sent to Recycle Bin
RESTORE Open Recycle Bin → select file/folder → File menu → Restore
note Deleted files go to Recycle Bin temporarily — not permanently gone until Bin is emptied
📊 Summary — Key Facts about File Systems
★ A file has a File Name and a File Extension
★ The OS identifies file type using the extension
★ Extensions are hidden by default but can be shown
★ Files are stored inside Folders inside Drives
★ Windows drives: C:, D:, E: … Linux: directories
★ Partitioning divides one disk into multiple logical drives
10 questions covering all Operating Systems topics. Click an answer to check immediately.
Question 0 / 10 answered
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📝 Practice Questions & Answers
Exam-style questions with full step-by-step answers. Try each one before revealing.
Q 01
What is an Operating System? Why is it important?
Definition: The Operating System is the software which facilitates interaction between the human user and the computer hardware. It manages all input, output, and computer memory.
Importance:
1. It is the sole software that manages the whole computer system
2. All application software runs on the Operating System
3. Provides instructions for installation and management of applications
4. Manages hardware, memory, devices, security and network
Without an OS, no software can run and the computer is unusable.
Q 02
Explain the booting process. What does "booting" mean?
Booting means loading the Operating System into RAM (main memory).
Step 1: User powers on → CPU activates the BIOS
Step 2: POST (Power On Self-Test) checks all hardware using CMOS memory
Step 3: Reads the MBR (Master Boot Record) via bootstrap loader firmware
Step 4: Loads the Operating System from boot drive into RAM
Step 5: OS takes control and displays the user interface
Q 03
Name and explain the four types of Operating Systems.
1. Single User OS — serves one person at a time. Example: MS-DOS
2. Multi-User OS — multiple users simultaneously. Example: Linux, Windows Server
3. Multi-Tasking OS — run multiple processes at once. Example: Windows 7/8, Ubuntu, Mac
4. Real Time OS — gives output with no observable delay. Example: ATM machines, calculators
Q 04
What are the two types of user interfaces? Compare CLI and GUI.
The two types are CLI (Command Line Interface) and GUI (Graphical User Interface).
CLI: Text-based · uses keyboard · requires memorising commands · uses less memory · faster for experts
The GUI is more convenient to the user than the CLI.
Q 05
What does WIMP stand for? Explain each component.
WIMP stands for the four components used in GUI Operating Systems:
W — Windows: Rectangular areas on screen showing open applications
I — Icons: Small images representing files, folders, or programs
M — Menus: Drop-down lists of commands available to the user
P — Pointer: On-screen cursor controlled by mouse or fingertip
Q 06
Explain the six hardware management services of an Operating System.
i. Process Management — allocates CPU time, memory and I/O devices; orders processes in sequence
ii. Memory Management — allocates RAM for each process; frees memory when process ends
iii. Device Management — manages peripheral devices through device controllers and device drivers
iv. File Management — creates, renames, moves, deletes files and folders
v. Security Management — protects from viruses, malware, unauthorised access
vi. Network Management — supports wired/wireless connectivity; enables remote access and data communication
Q 07
What is disk partitioning? Why is it needed? Give three reasons.
Disk Partitioning: The process of dividing one physical hard drive into multiple logical drives (partitions).
Reasons for partitioning:
1. To save different types of data in different places (software in C:, data in D:)
2. To install more than one OS on the same machine (dual-boot: Windows + Ubuntu)
3. To meet OS requirements (some OS need a dedicated partition)
⚠️ Re-partitioning deletes all data — always take a backup first!
Q 08
What is defragmentation? Why is it needed? Is it needed in Linux?
Fragmentation: When a large file is broken into pieces and stored in different parts of a disk. Defragmentation: Rearranges scattered pieces of data so files are stored contiguously, making the disk more efficient.
Why needed: Fragmented files take longer to read → computer slows down
When to use: When the computer is noticeably slow (fragmentation may be the cause)
Linux: Does NOT need defragmentation — Linux leaves space between files and can relocate files automatically. Very little fragmentation occurs.
Q 09
What is a file extension? Give five examples with their file types.
A file extension is the part after the full-stop (.) in a file name. The OS uses it to identify the file type.
File name structure: name.extension
.exe → Executable / Program file
.docx → Microsoft Word Document
.xlsx → Microsoft Excel Spreadsheet
.pptx → Microsoft PowerPoint Presentation
.jpg → JPEG Image file
Q 10
What is the difference between Ubuntu (Linux) and Windows in how they label drives?
Windows: Each partition is labelled with a letter — C:, D:, E: etc. The first partition is always C:. External drives (USB, DVD) get the next available letter.
Linux/Ubuntu: ALL partitions, multimedia drives, and flash drives appear as individual folders called Directories.
In Linux you will NOT see drive letters like C:, D: etc. Everything is accessed through the directory tree starting from the root (/).
💡 Study Tips
1
Remember the booting sequence. Power ON → BIOS → POST → MBR → Bootstrap → OS loads into RAM. Each acronym: BIOS, POST, MBR are commonly tested.
2
Know all 4 OS types with examples. Single (MS-DOS), Multi-User (Linux), Multi-Tasking (Windows 7), Real Time (ATM). Always give the example — exam marks go there.
3
WIMP = Windows, Icons, Menus, Pointer. This acronym is always asked. Remember it as a word: W-I-M-P.
4
6 hardware management services. Process, Memory, Device, File, Security, Network. Use the first letters: P-M-D-F-S-N to remember them.
5
Partition vs Format vs Defrag. Partition = divide; Format = prepare to store; Defrag = reorganise scattered files. All three delete data if not careful — backup first!