1 Types and Components of Computer Systems
1.1 Hardware, Firmware and Software
1.1.1 Hardware – the physical components
- Central Processing Unit (CPU) – the “brain” of the computer; it carries out the fetch‑decode‑execute cycle and coordinates all other components.
- Internal memory (primary storage)
- Random‑Access Memory (RAM) – volatile, read‑write memory that holds programmes and data currently being processed.
- Read‑Only Memory (ROM) – non‑volatile memory that stores permanent instructions such as the firmware used to start the computer.
- Input/Output (I/O) devices – keyboards, mouse, touch‑screen, printers, scanners, network cards, etc.
- Backing (secondary) storage – non‑volatile devices that retain data when power is removed (see 1.1.4 for a detailed classification).
1.1.2 Firmware
Firmware is low‑level software stored in non‑volatile memory (usually ROM or flash) that initialises the hardware and launches the operating system. It provides the first instructions the computer executes after power‑on.
- Typical examples: BIOS (Basic Input/Output System) and UEFI (Unified Extensible Firmware Interface) in personal computers; bootloaders in embedded devices.
- Purpose: hardware configuration, power‑on self‑test (POST), and handing control over to the OS.
1.1.3 Analogue and Digital Data
- Analogue data – continuous signals that can take any value within a range (e.g., sound waves, light intensity).
- Digital data – discrete values represented by binary digits (bits) 0 and 1.
- Conversion is required because computers operate digitally; analogue‑to‑digital converters (ADCs) and digital‑to‑analogue converters (DACs) perform this translation (e.g., microphone → ADC, speaker → DAC).
1.1.4 Storage Devices and Media
Secondary storage can be grouped by the technology used to record data.
Classification of storage media| Category | Typical devices | Key characteristics |
|---|
| Magnetic | Hard‑disk drives (HDD), magnetic tape, floppy disks | High capacity, relatively low cost, slower access time, vulnerable to magnetic fields. |
| Optical | CD‑ROM, DVD, Blu‑ray | Read‑only or write‑once, good for distribution, slower than magnetic, limited rewrites. |
| Solid‑state | Solid‑state drives (SSD), USB flash drives, memory cards (SD, micro‑SD) | Fast access, no moving parts, lower power consumption, higher cost per GB. |
These devices store programmes, data files, and the operating system itself.
1.1.5 Software – system vs. application
- System software – manages hardware and provides a platform for other software.
- Operating systems, device drivers, utility programmes, and firmware.
- Examples: Microsoft Windows, macOS, Linux, Android, iOS, BIOS/UEFI.
- Application software – programmes that enable users to perform specific tasks.
- Word processors, spreadsheets, web browsers, games, graphics editors, etc.
- Examples: Microsoft Word, Adobe Photoshop, Google Chrome.
1.2 Operating Systems (OS)
1.2.1 What is an operating system?
An operating system is the core system software that:
- Manages hardware resources (CPU, memory, I/O, storage).
- Provides a user interface (CLI, GUI, dialogue‑based, gesture‑based).
- Offers services to application software (file management, security, networking).
1.2.2 User‑interface categories
User‑interface types| Interface type | Typical devices / examples | Advantages | Disadvantages |
|---|
| Command‑Line Interface (CLI) | Text‑based terminals – MS‑DOS, Linux shell | Low resource use; powerful scripting & automation | Steep learning curve; less intuitive for beginners |
| Graphical User Interface (GUI) | Desktop OSes – Windows, macOS, GNOME, KDE | Visually intuitive; supports multitasking with windows | Higher CPU/RAM demand; can be slower on low‑end hardware |
| Dialogue‑based Interface | Touch‑screen kiosks, ATMs, some mobile apps | Step‑by‑step guidance; reduces input errors | Limited flexibility; many screens may be needed for complex tasks |
| Gesture‑based Interface | Smartphones, tablets, gaming consoles (e.g., iOS “swipe”, Android “pinch”) | Natural interaction; ideal for mobile devices | Requires specialised hardware; less precise for detailed work |
1.2.3 Classification of OS types
- Single‑User, Single‑Task – one user, one programme at a time (e.g., early MS‑DOS).
- Single‑User, Multi‑Task – one user can run several programmes simultaneously (e.g., Windows, macOS, Android).
- Multi‑User – many users share the same computer resources, usually via network terminals (e.g., UNIX, Linux, Windows Server).
- Real‑Time OS (RTOS) – guarantees deterministic response times for critical applications (e.g., VxWorks, QNX).
- Network Operating System (NOS) – provides file‑sharing, printer sharing and remote login services over a network (e.g., Novell NetWare, Windows Server).
- Mobile Operating System – optimised for handheld devices with touch input and power‑saving features (e.g., Android, iOS).
1.2.4 Advantages and Disadvantages of OS Types
Pros and cons of the main OS classifications| OS Type | Advantages | Disadvantages |
|---|
| Single‑User, Single‑Task | - Very simple design – easy to learn and use.
- Low hardware requirements (CPU, RAM, storage).
| - Only one programme can run at a time – poor productivity.
- Unsuitable for modern multitasking workloads.
|
| Single‑User, Multi‑Task | - Supports multitasking – several applications can run simultaneously.
- Broad software compatibility and rich GUIs.
- Well suited to personal and office environments.
| - Higher demand on CPU, RAM and storage.
- System instability may occur if resources are exhausted.
|
| Multi‑User | - Efficient resource sharing reduces overall hardware cost.
- Centralised administration, security and backup.
- Easily scalable for growing organisations.
| - Complex configuration and ongoing maintenance.
- Requires more powerful server‑class hardware.
- Performance may degrade under heavy simultaneous load.
|
| Real‑Time OS (RTOS) | - Deterministic, predictable response times – essential for safety‑critical systems.
- High reliability and stability.
| - Specialised; limited availability of general‑purpose applications.
- Often more expensive and harder to program.
|
| Network OS (NOS) | - Facilitates file, printer and resource sharing across a LAN.
- Centralised security policies and user management.
| - System depends on network availability – outages affect many users.
- Requires skilled network administration.
|
| Mobile OS | - Optimised for low power consumption – long battery life.
- Touch‑friendly, gesture‑based interfaces.
- Large ecosystem of apps for a wide range of tasks.
| - Limited multitasking compared with desktop OSes.
- Fragmentation – many device models, OS versions, and hardware capabilities.
- Security risks associated with third‑party app stores.
|
1.3 Network Devices (cross‑reference)
Network hardware such as routers, switches, hubs, network interface cards (NICs), Wi‑Fi adapters and Bluetooth modules are covered in detail in Section 2 of the notes. These devices work together with Network Operating Systems to provide connectivity and resource sharing.
1.4 Summary
Choosing the appropriate operating system involves matching its characteristics—resource requirements, multitasking capability, user‑interface style, real‑time response, networking services, and mobility—to the intended purpose and the hardware available. The Cambridge IGCSE 0417 syllabus expects learners to:
- Identify and describe CPU, RAM, ROM, I/O devices, and the three categories of secondary storage.
- Explain the role of firmware as low‑level software stored in non‑volatile memory.
- Distinguish between analogue and digital data and why conversion is needed.
- Classify operating systems (single‑user, multi‑user, RTOS, NOS, mobile) and evaluate their advantages and disadvantages.
- Recognise different user‑interface types and their suitability for various tasks.
By understanding these concepts, students can make informed, syllabus‑aligned decisions about which OS best fits a given computing environment.