System Software
This lesson covers the types of system software required by the OCR H446 specification, including the operating system, utility software and their roles. You must understand the distinction between system software and application software, and be able to describe the purpose of key utility programs.
What Is System Software?
System software is any software that manages the computer's hardware and provides a platform for application software to run. It acts as an intermediary between the user, the applications and the hardware.
System Software vs Application Software
| Feature | System Software | Application Software |
|---|
| Purpose | Manages hardware and provides services for applications | Performs specific tasks for the user |
| Examples | Operating system, device drivers, utilities, compilers | Word processor, web browser, games, spreadsheet |
| User interaction | Often runs in the background; user may not interact directly | User interacts directly |
| Installed by | Usually pre-installed or installed as part of setup | Installed by the user as needed |
The Operating System (OS)
The operating system is the most important piece of system software. It manages all the hardware resources and provides an environment in which application software can run. Without an OS, the user would need to manage hardware directly using machine code.
Key Roles of the OS
| Role | Description |
|---|
| Resource management | Manages and allocates CPU time, memory, storage and I/O devices among competing processes |
| Process management | Creates, schedules, suspends and terminates processes. Handles multi-tasking |
| Memory management | Allocates RAM to processes, manages virtual memory, handles paging and segmentation |
| File management | Organises files into a directory structure, handles read/write operations, manages permissions |
| I/O management | Controls communication between the CPU and peripheral devices using device drivers |
| Security | Manages user accounts, passwords, access permissions and encryption |
| User interface | Provides a way for users to interact with the computer (GUI, CLI) |
| Error handling | Detects and handles errors (e.g. division by zero, missing files, hardware failures) |
| Networking | Manages network connections, protocols and data transfer |
Types of Operating System
| Type | Description | Example |
|---|
| Multi-tasking | Can run multiple processes apparently simultaneously by switching between them rapidly | Windows, macOS, Linux |
| Multi-user | Multiple users can use the system simultaneously, each with their own session and permissions | Unix, Linux servers |
| Real-time | Guarantees responses within strict time limits; used in safety-critical embedded systems | FreeRTOS, VxWorks |
| Distributed | Manages a group of separate computers so they appear as a single system | Google's distributed systems |
| Embedded | Lightweight OS for dedicated hardware with limited resources | Embedded Linux, Zephyr, RTOS |
| Mobile | Optimised for touchscreen devices with limited battery and processing power | Android, iOS |
Utility Software
Utility software consists of small programs that perform specific maintenance or optimisation tasks to keep the computer running efficiently. Utilities are system software — they support the OS and manage hardware, rather than performing tasks for the end user.
Disk Defragmentation
| Aspect | Detail |
|---|
| What it does | Rearranges fragmented data on a hard disk so that files are stored in contiguous (adjacent) sectors |
| Why it is needed | Over time, as files are created, modified and deleted, data becomes scattered across the disk (fragmentation). The read/write head must move more, increasing seek time and slowing performance |
| How it works | The utility reads fragmented files, copies them to temporary space, and rewrites them in contiguous blocks. It also consolidates free space into a single block |
| Not needed for SSDs | SSDs have no moving parts and access any location equally fast. Defragmentation provides no benefit for SSDs and can actually reduce their lifespan by causing unnecessary writes |
Before defragmentation:
[A][B][A][ ][C][A][B][ ][C][ ]
After defragmentation:
[A][A][A][B][B][C][C][ ][ ][ ]
Compression
| Aspect | Detail |
|---|
| What it does | Reduces the file size of one or more files |
| Why it is needed | Smaller files use less storage space, transfer faster over networks, and can be attached to emails within size limits |
| Types of compression | Lossless — the original data can be perfectly reconstructed (e.g. ZIP, PNG, FLAC). Lossy — some data is permanently discarded to achieve greater compression (e.g. JPEG, MP3, MP4) |
| Type | How It Works | Use Case |
|---|
| Lossless | Identifies and removes redundancy (e.g. run-length encoding, Huffman coding, dictionary compression). The original file can be perfectly restored | Text files, executables, archives, medical images |
| Lossy | Removes data that is less perceptible to humans (e.g. high-frequency sounds, subtle colour variations). Original cannot be fully restored | Photos (JPEG), music (MP3), video (MP4) |
Backup
| Aspect | Detail |
|---|
| What it does | Creates copies of files and data so they can be restored if the originals are lost, corrupted or accidentally deleted |
| Why it is needed | Hardware failure, malware, accidental deletion, natural disasters and theft can all cause data loss |
| Backup Type | Description | Advantages | Disadvantages |
|---|
| Full backup | Copies ALL files every time | Simple to restore — everything is in one backup | Takes the longest time and most storage space |
| Incremental backup | Copies only files that have changed since the last backup (full or incremental) | Fast; uses least storage | Restoring requires the last full backup PLUS every subsequent incremental backup |
| Differential backup | Copies all files that have changed since the last full backup | Faster than full; restoring needs only the last full backup + last differential | Takes more space than incremental; gets larger over time |
Encryption
| Aspect | Detail |
|---|
| What it does | Converts readable data (plaintext) into an unreadable format (ciphertext) using an encryption algorithm and a key |
| Why it is needed | Protects sensitive data from unauthorised access if a device is lost, stolen or intercepted during transmission |
| Decryption | The process of converting ciphertext back to plaintext using the correct key |
| Encryption Type | Description |
|---|
| Symmetric | The same key is used to encrypt and decrypt. Fast but the key must be shared securely (e.g. AES) |
| Asymmetric | Uses a key pair — a public key (to encrypt) and a private key (to decrypt). Slower but solves the key distribution problem (e.g. RSA) |
Other Common Utilities
| Utility | Purpose |
|---|
| Antivirus / anti-malware | Scans files and processes for known malware signatures and suspicious behaviour; quarantines or removes threats |
| Disk cleanup | Removes temporary files, cache data and other unnecessary files to free up storage space |
| File manager | Provides a graphical interface for navigating, copying, moving, renaming and deleting files |
| System monitor / task manager | Displays running processes, CPU usage, memory usage and network activity; allows processes to be terminated |
| Disk formatter | Prepares a storage device for use by creating a file system structure |
Exam Tip: When asked to describe utility software, always state: (1) what the utility does, (2) why it is needed, and (3) how it benefits the user or system. A one-sentence answer will not score full marks.
Key Terms
| Term | Definition |
|---|
| System software | Software that manages hardware and provides a platform for application software |
| Operating system | The main system software that manages hardware resources and provides an interface for applications |
| Utility software | Small programs that perform maintenance and optimisation tasks |
| Fragmentation | When files are stored in non-contiguous sectors, reducing performance on HDDs |
| Defragmentation | Rearranging data so files are stored in contiguous sectors |
| Lossless compression | Compression that allows perfect reconstruction of the original data |
| Lossy compression | Compression that permanently removes some data for greater file size reduction |
| Encryption | Converting plaintext into ciphertext using an algorithm and key |
Summary
- System software manages hardware and supports application software. The OS is the most important example.
- The OS handles process management, memory management, file management, I/O management, security and the user interface.
- Utility software includes defragmentation (reorganise HDD data), compression (reduce file sizes), backup (protect against data loss), encryption (protect data confidentiality) and antivirus (detect and remove malware).