Operating Systems

🖥️ What is a User Interface?

The user interface (UI) is how users interact with the computer. The operating system provides the interface that allows users to give commands and receive feedback.

Features of a User Interface

Feature	GUI	CLI
Ease of learning	Easy - visual and intuitive	Difficult - must learn commands
Speed of use (expert)	Slower - many clicks needed	Faster - direct commands
Memory/processor usage	Higher - graphics need resources	Lower - text only
Automation	Limited	Excellent - scripts can automate tasks
Error prevention	Better - visual feedback, confirmations	Worse - easy to make typos

🧠 What is Memory Management?

Memory management is how the OS controls and coordinates computer memory (RAM). It allocates memory to programs, keeps track of what memory is in use, and reclaims memory when programs close.

Key Memory Management Functions

Function	What It Does	Why It's Important
Allocation	Assigns portions of RAM to applications when they start	Applications need memory to store data and instructions
Tracking	Keeps a record of which memory locations are in use and which are free	Prevents programs from overwriting each other's data
Protection	Prevents one program from accessing another program's memory	Security and stability - one crash doesn't affect others
Deallocation	Reclaims memory when programs close or no longer need it	Frees up memory for other applications to use

Transfer of Data Between Memory

The OS manages the movement of data between different types of storage:

• Secondary Storage → RAM: When you open a program, the OS loads it from the hard drive/SSD into RAM
• RAM → CPU Cache: Frequently used data is copied closer to the CPU for faster access
• RAM → Secondary Storage: When you save a file, data moves from RAM to permanent storage
• Virtual Memory: When RAM is full, the OS can use part of the hard drive as temporary RAM

How Multitasking Works

Multitasking allows multiple programs to run "simultaneously" on a computer. The OS achieves this through:

🖨️ What is Peripheral Management?

Peripherals are external devices connected to a computer (printers, keyboards, mice, monitors, USB drives, etc.). The OS manages communication between the CPU and these devices.

The Challenge

Each peripheral device is different - a printer works differently from a keyboard. The OS needs to:

• Detect when devices are connected or disconnected
• Establish communication with each device
• Transfer data to and from devices
• Handle multiple devices wanting attention at once

Device Drivers

A driver is a small program that translates between the operating system and a specific hardware device. It allows the OS to communicate with hardware without needing to know exactly how each device works internally.

Component	Role
Application	Says "print this document"
Operating System	Receives print request, passes to printer driver
Printer Driver	Translates request into specific commands the printer understands
Printer Hardware	Receives commands and prints the document

Data Transfer Between Devices and Processor

The OS manages how data flows between peripherals and the CPU:

• Interrupts: Devices signal the CPU when they need attention (e.g., keyboard key pressed)
• Buffers: Temporary storage areas that hold data during transfer (e.g., print queue)
• I/O Scheduling: OS decides which device requests to handle first
• Plug and Play: OS automatically detects new devices and loads appropriate drivers

👤 What is User Management?

User management controls who can access the computer, what they can do, and keeps each user's data separate and secure. This is essential for shared computers (schools, offices, families).

User Management Functions

Function	What It Does	Example
Account Allocation	Creates and manages user accounts	Creating a new student account "jsmith" on the school network
Authentication	Verifies user identity (login)	Checking username and password match records
Access Rights	Controls what each user can access and modify	Students can read shared resources but not delete them
Resource Quotas	Limits how much storage/resources each user can use	Each student gets 500MB of network storage
Security Policies	Enforces password rules and security settings	Passwords must be 8+ characters and changed every 90 days
Audit Logging	Records user activities for security monitoring	Logging when users log in/out and what files they access

Types of User Accounts

Access Rights in Detail

The OS controls permissions at multiple levels:

• File Level: Who can read, write, or execute specific files
• Folder Level: Who can view folder contents, create/delete files within
• Application Level: Who can run certain programs
• System Level: Who can change system settings, install software

📁 What is File Management?

The file management system organises how data is stored, retrieved, and organised on storage devices. It provides the folder structure and file operations users interact with daily.

Key File Management Features

Feature	What It Does	Example
Naming	Assigns names to files so they can be identified	homework.docx, photo_001.jpg
Extensions	File type indicators that tell OS which program to use	.docx = Word, .pdf = PDF reader, .py = Python
Folder Organisation	Hierarchical structure for grouping related files	Documents → School → Year 10 → Computing
Moving/Copying	Relocating or duplicating files between locations	Moving photos from Downloads to Pictures folder
Saving	Writing data from RAM to permanent storage	Pressing Ctrl+S to save your document
Deleting	Removing files (often to Recycle Bin first)	Deleting old files to free up space
Searching	Finding files by name, content, or properties	Searching for "homework" to find all matching files
Properties/Metadata	Storing information about files (size, date, type)	Date created: 15/01/2025, Size: 2.4 MB

File Paths

A file path is the complete location of a file in the folder hierarchy:

How File Management Works

• File System: The OS uses a file system (like NTFS on Windows or APFS on Mac) to organise data on the disk
• File Allocation Table: The OS keeps a record of where each file is physically stored on the disk
• Fragmentation: When files are deleted, gaps appear. The OS may spread new files across these gaps (fragmentation)
• Permissions: File management integrates with user management to control who can access each file

File Operations