Operating Systems

Operating System Fundamentals

What Is an Operating System?

An Operating System (OS) is the most important software installed on a computer. It manages the computer’s hardware resources, provides a platform for running applications, and allows users to interact with the computer.

Without an operating system, hardware components such as the processor, memory, storage devices, keyboard, and monitor cannot work together effectively.

The operating system acts as an intermediary between:

Every computing device—including desktops, laptops, tablets, smartphones, servers, gaming consoles, and many IoT devices—requires an operating system.

Primary Functions of an Operating System

The operating system performs many critical tasks.

Its primary responsibilities include:

Without these functions, computers would not operate efficiently.

Hardware Resource Management

The operating system coordinates communication between software and hardware.

Examples include:

The operating system determines which programs receive system resources and when they receive them.

Running Applications

Applications depend on the operating system to access hardware.

For example:

A word processor does not communicate directly with the printer.

Instead:

Word Processor → Operating System → Printer Driver → Printer

This design improves compatibility and simplifies software development.

Memory Management

Memory management is one of the operating system’s most important responsibilities.

The OS:

Proper memory management improves system stability and performance.

File Management

The operating system organizes information into:

It manages:

Modern operating systems also support advanced file systems with security and recovery features.

Security Management

Operating systems protect computers by providing:

Security features help prevent unauthorized access to data and system resources.

Device Management

The operating system communicates with hardware through device drivers.

Examples include:

Without the correct driver, hardware may not function correctly.

Networking Services

Modern operating systems provide built-in networking capabilities.

Examples include:

Networking allows computers to communicate with other devices.

Multitasking

Multitasking allows multiple applications to run simultaneously.

Examples:

The operating system rapidly switches processor time among programs, creating the appearance that they are running at the same time.

Components of an Operating System

An operating system contains several major components.

These include:

Each component performs a specialized function.

Kernel

The kernel is the core of the operating system.

It is responsible for:

Because the kernel operates with the highest level of system privileges, it has direct access to hardware resources.

Shell

The shell provides a way for users to interact with the operating system.

A shell may be:

The shell interprets user commands and sends them to the kernel for execution.

User Interface (UI)

A User Interface (UI) allows people to interact with a computer.

Two primary interface types are used.

Graphical User Interface (GUI)

A Graphical User Interface (GUI) allows users to interact using visual elements.

Examples include:

Advantages:

Examples:

Command-Line Interface (CLI)

A Command-Line Interface (CLI) requires users to type commands.

Examples include:

Advantages:

Disadvantages:

GUI vs CLI
GUICLI
Uses windows and iconsUses typed commands
Easier for beginnersBetter for advanced users
More visualMore flexible
Requires more system resourcesRequires fewer resources
Mouse-friendlyKeyboard-focused
Device Drivers

A device driver is software that enables the operating system to communicate with specific hardware.

Every hardware device requires an appropriate driver.

Examples include:

Without a compatible driver, the operating system may not recognize or properly use the hardware.

Types of Operating Systems

Operating systems are designed for different purposes.

Common categories include:

Desktop Operating Systems

Desktop operating systems support personal computers used by individuals.

Common desktop operating systems include:

Microsoft Windows

Windows is the most widely used desktop operating system.

Characteristics:

macOS

macOS is Apple’s desktop operating system.

Characteristics:

Linux

Linux is an open-source operating system available in many distributions.

Examples include:

Characteristics:

Mobile Operating Systems

Mobile operating systems are designed for smartphones and tablets.

Examples:

These operating systems are optimized for:

Server Operating Systems

Server operating systems manage network resources and provide services to multiple users.

Common functions include:

Examples include:

Embedded Operating Systems

Embedded operating systems run on dedicated devices designed for specific tasks.

Examples include:

Embedded operating systems emphasize reliability and efficiency.

Real-Time Operating Systems (RTOS)

A Real-Time Operating System (RTOS) processes data within strict time limits.

Applications include:

Unlike general-purpose operating systems, RTOS platforms prioritize predictable response times.

32-bit vs 64-bit Operating Systems

Operating systems are available in different processor architectures.

32-bit Operating Systems

Characteristics:

64-bit Operating Systems

Characteristics:

Most computers today use 64-bit operating systems.

System Requirements

Before installing an operating system, verify that the computer meets the minimum hardware requirements.

Common requirements include:

Meeting only the minimum requirements allows the OS to run, but exceeding them generally results in better performance.

The Boot Process

The boot process is the sequence of steps that occurs when a computer starts.

Typical steps include:

  1. Power is turned on.
  2. Firmware (BIOS or UEFI) performs a Power-On Self-Test (POST).
  3. Hardware is initialized.
  4. A boot device is located.
  5. The bootloader is loaded.
  6. The operating system kernel loads into memory.
  7. System services start.
  8. The login screen appears.

Understanding the boot process helps troubleshoot startup problems.

BIOS (Basic Input/Output System)

BIOS is traditional motherboard firmware responsible for starting the computer.

Functions include:

Limitations include:

UEFI (Unified Extensible Firmware Interface)

UEFI is the modern replacement for BIOS.

Advantages include:

Most modern computers use UEFI instead of BIOS.

BIOS vs UEFI
BIOSUEFI
Older firmwareModern firmware
Text-based setupGraphical interface
Slower startupFaster startup
Legacy boot supportSecure Boot support
Limited disk size supportSupports very large drives
Secure Boot

Secure Boot is a UEFI security feature that helps prevent unauthorized software from loading during startup.

Secure Boot verifies that bootloaders and operating system components are digitally signed before allowing them to execute.

Benefits include:

Boot Sequence

The boot sequence determines the order in which the computer searches for bootable devices.

Common boot devices include:

Changing the boot order is often necessary when installing a new operating system.

Choosing the Appropriate Operating System
RequirementRecommended Operating System
Home userWindows or macOS
StudentWindows, ChromeOS, or macOS
BusinessWindows or Linux
ServerWindows Server or Linux
Embedded deviceEmbedded OS
Industrial automationRTOS

Key Terms

Exam Tips

Operating System Interfaces, User Accounts, and System Management

Managing an Operating System

After an operating system is installed, it must be managed regularly to ensure stability, security, and performance.

Common management tasks include:

Although Windows, macOS, and Linux use different interfaces, the overall management tasks are very similar.

Windows User Interface

Microsoft Windows uses a Graphical User Interface (GUI) that allows users to interact with the operating system through windows, icons, menus, and buttons.

The Windows interface is designed to make navigation intuitive for both beginners and advanced users.

Desktop

The Desktop is the primary workspace displayed after a user signs in.

It commonly contains:

Users can personalize the desktop with backgrounds, themes, and icons.

Start Menu

The Start Menu provides quick access to:

In Windows 11, the Start Menu appears centered by default but can be repositioned.

Taskbar

The Taskbar provides quick access to frequently used applications.

It contains:

The taskbar allows users to switch quickly between open programs.

Notification Area (System Tray)

The notification area displays:

Many applications continue running here even when their main windows are closed.

File Explorer

File Explorer allows users to manage files and folders.

Common tasks include:

File Explorer is the primary file management tool in Windows.

Settings

The Settings application is used to configure Windows.

Users can modify:

Windows 11 continues moving configuration options from the older Control Panel into Settings.

Control Panel

Although many features have moved to Settings, Control Panel remains available for managing legacy system components.

Common Control Panel functions include:

macOS Interface

macOS provides a clean graphical interface optimized for Apple hardware.

Major interface components include:

Finder

Finder is macOS’s file management application.

It performs functions similar to Windows File Explorer.

Users can:

Dock

The Dock provides quick access to:

Applications can be pinned for easy access.

Menu Bar

Located at the top of the screen, the Menu Bar provides:

Unlike Windows, the Menu Bar changes depending on the active application.

System Settings

System Settings allows users to configure:

Linux Interface

Linux distributions vary, but most include:

Popular desktop environments include:

Although layouts differ, the overall functionality is similar.

Terminal

The Terminal provides command-line access to Linux.

Common uses include:

Many Linux administrators rely heavily on the terminal because it provides precise control over the operating system.

User Accounts

Operating systems support multiple user accounts so different people can safely use the same computer.

Each user account stores personalized information such as:

Each account is isolated to help protect user data and system settings.

User Privileges and Permissions

A privilege is a right assigned to a user account that allows certain actions.

A permission determines what resources a user may access.

Permissions help protect:

Administrators can assign different permission levels to different users or groups.

Administrator Account

The Administrator account has the highest level of system access.

Typical administrative tasks include:

Administrator accounts should be used only when elevated privileges are required to reduce security risks.

Standard User Account

A Standard User account is intended for everyday computing.

Standard users can typically:

However, they generally cannot:

Using a standard account for daily activities helps protect the system from accidental or malicious changes.

Guest Account

A Guest account provides very limited access for temporary users.

Characteristics include:

Many modern operating systems disable the guest account by default because of security concerns.

Creating User Accounts

Only users with administrative privileges can typically create new user accounts.

The basic process is similar across operating systems:

  1. Open the account management settings.
  2. Select Add User or Create Account.
  3. Enter a username.
  4. Set a password.
  5. Choose the account type (Administrator or Standard User).
  6. Save the account.

Windows, macOS, and Linux all provide graphical tools for managing users, although the exact steps differ.

Password Protection

Every user account should be protected with a strong password.

A strong password should:

Strong passwords reduce the risk of unauthorized access. Guest accounts, when enabled, may have different security requirements depending on the operating system.

Applications

An application is software designed to help users perform specific tasks.

Examples include:

Applications rely on the operating system for access to hardware resources.

Processes

A process is a program that is currently running.

Each running application creates one or more processes.

The operating system allocates:

to each process.

Foreground and Background Processes

Foreground Processes

These are programs currently being used by the user.

Examples:

Background Processes

These operate without direct user interaction.

Examples:

Many background processes are essential for normal system operation.

Services

A service is a specialized background program that starts automatically and performs system functions.

Examples include:

Unlike ordinary applications, services often start automatically during system startup.

Task Manager (Windows)

Task Manager is a Windows utility used to monitor and manage running programs and system resources.

It allows users to:

Task Manager is one of the most valuable troubleshooting tools for Windows.

Common Task Manager Tabs

Processes

Displays currently running applications and background processes.

Performance

Shows:

Startup

Displays applications that automatically launch when Windows starts.

Disabling unnecessary startup applications can improve boot time.

Users

Displays currently signed-in users and their resource usage.

Device Manager

Device Manager is used to view and manage installed hardware.

Administrators can:

Devices with missing or incorrect drivers often display warning symbols.

Storage Management

Operating systems provide tools for managing storage devices.

Common tasks include:

Proper storage management helps maintain system performance.

Memory Management

The operating system constantly monitors RAM usage.

If physical memory becomes limited, the OS may use virtual memory stored on the storage drive to temporarily extend available memory.

Although virtual memory allows more applications to remain open, it is significantly slower than physical RAM.

Best Practices for Managing an Operating System

Key Terms

Exam Tips

File Systems, Storage Management, and Operating System Maintenance

File Systems

A file system is the method an operating system uses to organize, store, retrieve, and manage files on a storage device.

Without a file system, the operating system would not know:

Each operating system supports one or more file systems optimized for different purposes.

Functions of a File System

A file system is responsible for:

Modern file systems also improve reliability, security, and performance.

NTFS (New Technology File System)

NTFS is the default file system used by modern versions of Microsoft Windows.

It was designed to provide improved reliability, security, and support for large storage devices.

Features

Because of these features, NTFS is recommended for internal Windows drives.

Advantages of NTFS

Disadvantages of NTFS

FAT32 (File Allocation Table 32)

FAT32 is an older file system that remains widely supported.

It is commonly used on:

Advantages of FAT32

Limitations of FAT32

Because of the 4 GB file size limit, FAT32 is not suitable for very large video files or disk images.

exFAT (Extended File Allocation Table)

exFAT was designed to replace FAT32 for removable storage.

It supports much larger files while maintaining excellent compatibility.

Common uses include:

Advantages of exFAT

Limitations of exFAT

exFAT is often the best choice for removable drives shared between Windows and macOS.

APFS (Apple File System)

APFS is Apple’s modern file system.

It replaced HFS+ on macOS and is also used on iOS, iPadOS, watchOS, and tvOS devices.

Features

APFS is optimized for flash storage and solid-state drives.

ext4 (Fourth Extended File System)

ext4 is one of the most widely used Linux file systems.

Features include:

Many Linux distributions use ext4 by default.

Comparison of Common File Systems
File SystemPrimary OSLarge File SupportPermissionsJournaling
NTFSWindowsYesYesYes
FAT32Windows, macOS, LinuxNo (4 GB limit)NoNo
exFATWindows, macOS, LinuxYesLimitedNo
APFSAppleYesYesYes
ext4LinuxYesYesYes
Files

A file is a collection of related data stored under a single name.

Examples include:

Every file has:

Folders (Directories)

A folder is a container used to organize files and other folders.

Benefits include:

Folders may contain:

Directory Structure

Operating systems organize storage into a hierarchical directory structure.

Example:

Documents
 ├── School
 │     ├── Notes.docx
 │     ├── Homework.pdf
 ├── Pictures
 ├── Videos

This structure allows users to organize information logically.

File Paths

A file path specifies the exact location of a file.

Example (Windows):

C:\Users\Student\Documents\Notes.docx

Example (Linux/macOS):

/home/student/Documents/Notes.docx

Absolute paths specify the full location, while relative paths describe a location relative to the current folder.

File Extensions

A file extension identifies the file type and often determines which application opens it.

Common examples include:

ExtensionFile Type
.docxMicrosoft Word document
.xlsxMicrosoft Excel workbook
.pptxMicrosoft PowerPoint presentation
.pdfPortable Document Format
.txtPlain text
.jpgJPEG image
.pngPNG image
.mp3Audio
.mp4Video
.zipCompressed archive
.exeWindows executable

Knowing file extensions helps users identify file formats and avoid accidentally running malicious executables.

File Permissions

File permissions determine who may:

Permissions help protect sensitive information from unauthorized access.

File Compression

Compression reduces file size to save storage space and speed up file transfers.

Common compressed formats include:

Advantages:

Compression is lossless for these archive formats, meaning the original data is preserved when extracted.

File Encryption

Encryption converts readable data into an unreadable format that can only be accessed with the correct key or credentials.

Benefits include:

Windows supports Encrypting File System (EFS) on NTFS volumes, while macOS and Linux provide their own encryption technologies.

Hidden Files

Hidden files are system or configuration files that are not displayed by default.

Reasons for hiding files include:

Users should exercise caution when modifying hidden files, as they may be required for proper system operation.

Backups

A backup is a copy of data stored separately from the original.

Backups protect against:

Regular backups are an essential part of any maintenance plan.

Types of Backups

Full Backup

Copies all selected data.

Advantages:

Disadvantages:

Incremental Backup

Copies only data that has changed since the last backup of any type.

Advantages:

Disadvantages:

Differential Backup

Copies all data changed since the last full backup.

Advantages:

Disadvantages:

System Restore

System Restore is a Windows feature that returns system files and settings to an earlier restore point.

It can help resolve issues caused by:

System Restore does not replace regular backups because it does not protect personal files.

Windows Update

Windows Update downloads and installs:

Keeping Windows updated helps improve security, compatibility, and stability.

Users should avoid delaying critical security updates unless there is a valid administrative reason.

Installing Software

Software should be installed only from trusted sources.

Typical installation steps:

  1. Download or insert installation media.
  2. Verify the software source.
  3. Run the installer.
  4. Accept the license agreement.
  5. Choose installation options.
  6. Complete installation.
  7. Restart the computer if required.

Always verify compatibility with the operating system before installing new software.

Uninstalling Software

Applications that are no longer needed should be removed properly using the operating system’s uninstall tools.

Benefits include:

Deleting an application’s folder manually does not always remove all components.

Disk Cleanup

Disk Cleanup removes unnecessary files, including:

Removing unnecessary files helps free storage space and improve system efficiency.

Disk Defragmentation

On traditional Hard Disk Drives (HDDs), files can become fragmented over time.

Disk Defragmentation reorganizes fragmented data so files are stored in contiguous locations, improving read performance.

Important: SSDs should not be manually defragmented because they access data differently and unnecessary defragmentation can reduce drive lifespan. Modern operating systems automatically optimize SSDs using appropriate methods.

General Maintenance Best Practices

Routine maintenance helps maintain performance, reliability, and security.

Key Terms

Exam Tips

Security and Troubleshooting

Operating System Security

One of the operating system’s primary responsibilities is protecting the computer, applications, and user data from unauthorized access and malicious software.

Modern operating systems provide several built-in security features, including:

These features work together to protect system resources and maintain data integrity.

Authentication

Authentication is the process of verifying a user’s identity before granting access to a system or resource.

Common authentication methods include:

Authentication ensures that only authorized users can access protected resources.

Authorization

After authentication, the operating system performs authorization.

Authorization determines:

Authentication answers “Who are you?”, while authorization answers “What are you allowed to do?”

Password Policies

Organizations often enforce password policies to improve security.

Common password requirements include:

Strong password policies reduce the likelihood of unauthorized access.

Password Best Practices

Users should:

Strong passwords remain one of the most effective defenses against unauthorized access.

Multi-Factor Authentication (MFA)

Multi-Factor Authentication (MFA) requires two or more forms of authentication.

Authentication factors include:

Something You Know

Something You Have

Something You Are

MFA significantly increases account security because compromising one factor alone is not sufficient.

User Account Control (UAC)

User Account Control (UAC) is a Windows security feature that helps prevent unauthorized system changes.

When an application attempts to perform an administrative action, Windows displays a confirmation prompt.

Examples include:

UAC helps prevent malware from making unauthorized changes without user approval.

Windows Firewall

A firewall monitors and filters network traffic entering and leaving a computer.

It helps block unauthorized connections while allowing legitimate communication.

Benefits include:

Windows includes Microsoft Defender Firewall by default.

Antivirus Software

Antivirus software detects, blocks, and removes malicious software.

Common threats include:

Modern antivirus programs provide:

Keeping antivirus definitions updated is essential for effective protection.

Operating System Updates

Operating system vendors regularly release updates to:

Automatic updates help ensure systems remain protected against newly discovered threats.

Safe Mode

Safe Mode starts Windows with only the essential drivers and services needed for basic operation.

It is commonly used to troubleshoot:

Because unnecessary drivers and startup applications are disabled, Safe Mode provides a simplified environment for diagnosis.

Windows Recovery Environment (WinRE)

The Windows Recovery Environment (WinRE) is a recovery platform used when Windows cannot start normally.

Common recovery tools include:

WinRE helps recover systems without reinstalling Windows in many situations.

Startup Problems

Common causes of startup failures include:

Typical troubleshooting steps include:

  1. Check hardware connections.
  2. Remove newly installed hardware.
  3. Boot into Safe Mode.
  4. Run Startup Repair.
  5. Restore the system to an earlier restore point.
  6. Repair the bootloader if necessary.
  7. Reinstall the operating system if other methods fail.
Performance Problems

A computer may perform poorly due to:

Regular maintenance helps reduce these issues.

Troubleshooting Slow Performance

Recommended steps include:

Always identify the root cause before replacing hardware.

Event Viewer

Event Viewer is a Windows utility that records system events and errors.

It stores logs for:

Administrators use Event Viewer to investigate crashes, failed logins, hardware issues, and software errors.

Common Event Log Categories

Application Log

Records events generated by applications.

Security Log

Records:

System Log

Records events generated by Windows components and device drivers.

Task Scheduler

Task Scheduler automates tasks by running programs at scheduled times or when specific events occur.

Examples include:

Automation reduces the need for manual intervention.

Resource Monitor

Resource Monitor provides detailed information about system resources.

It monitors:

Compared to Task Manager, Resource Monitor provides more detailed diagnostic information.

Performance Monitor

Performance Monitor tracks long-term system performance using counters and graphs.

Administrators use it to identify:

Performance Monitor is especially useful for diagnosing intermittent performance problems.

Cross-Platform Comparison
FeatureWindowsmacOSLinux
DeveloperMicrosoftAppleOpen-source community
GUIYesYesYes
CLICommand Prompt / PowerShellTerminalTerminal
Default File SystemNTFSAPFSext4 (common)
HardwareMany manufacturersApple onlyMany manufacturers
Software AvailabilityExtensiveExtensiveVaries by distribution
Choosing the Appropriate Operating System
UserRecommended OS
Home UserWindows or macOS
StudentWindows, macOS, or ChromeOS
Business OfficeWindows
Software DeveloperLinux or macOS
Server AdministratorWindows Server or Linux
Embedded DeviceEmbedded OS
Industrial AutomationRTOS
Best Practices for Operating System Security

Key Terms

Exam Tips

Operating Systems

User Accounts

File Systems

Security

Troubleshooting

Maintenance