Computer Fundamentals — Hardware, Software and Networking
A computer is a programmable machine that accepts input, processes data according to instructions, stores results and produces output. The same architectural idea — input → process → storage → output — describes everything from a desktop PC to a smartphone to a supercomputer.
The classic computer design proposed by John von Neumann in 1945: a single memory stores both data and instructions, and a central processing unit fetches, decodes and executes those instructions sequentially. Almost every modern computer follows this scheme.
Hardware — the physical parts
Hardware divides into four functional groups:
- Input devices — keyboard, mouse, microphone, scanner, camera.
- Processing — the Central Processing Unit (CPU), with its Arithmetic Logic Unit (ALU), Control Unit (CU) and registers. The clock speed (measured in GHz) sets the pace of execution.
- Memory and storage:
- RAM (Random Access Memory) — fast, volatile, working memory.
- ROM (Read-Only Memory) — non-volatile, holds firmware like the BIOS.
- Secondary storage — hard disk drive (HDD), solid-state drive (SSD), flash drives, optical discs, cloud storage.
- Output devices — monitor, printer, speakers, projector.
A bus is the set of wires that carries data between these components.
Units of digital information
A bit (binary digit) is 0 or 1 — the smallest unit. Eight bits make one byte.
| Unit | Approximate size |
|---|---|
| 1 kilobyte (KB) | 1,024 bytes ≈ 10³ bytes |
| 1 megabyte (MB) | 1,024 KB ≈ 10⁶ bytes |
| 1 gigabyte (GB) | 1,024 MB ≈ 10⁹ bytes |
| 1 terabyte (TB) | 1,024 GB ≈ 10¹² bytes |
| 1 petabyte (PB) | 1,024 TB ≈ 10¹⁵ bytes |
The decimal (SI) prefixes (KB = 1000) and the binary prefixes (KiB = 1024) differ slightly. Storage manufacturers usually quote decimal sizes, while operating systems often report binary, which is why a "1 TB" disk shows as ~931 GB in Windows.
Software — instructions for the hardware
Software is broadly split into:
- System software — the operating system (Windows, Linux, macOS, Android, iOS), device drivers, utilities.
- Application software — programs that solve user problems: word processors, browsers, spreadsheets, games, banking apps.
- Programming languages and tools — compilers, interpreters, integrated development environments.
A programming language lets humans write instructions in symbolic form. High-level languages (Python, Java, C++) are translated into low-level machine code for the CPU by a compiler or interpreter.
Computer networking
A network is two or more computers connected to share data and resources.
- LAN (Local Area Network) — confined to a building or campus (e.g. an office Wi-Fi).
- MAN (Metropolitan Area Network) — covers a city.
- WAN (Wide Area Network) — spans regions or continents; the Internet is the largest WAN.
- Topology — physical/logical arrangement: bus, star, ring, mesh.
- Protocols — agreed rules: TCP/IP is the foundation of the Internet, HTTP/HTTPS for the web, SMTP for email, FTP for file transfer.
How the Internet works (the short version)
- Each device on the network has an IP address (e.g. 192.0.2.34).
- The Domain Name System (DNS) translates human-readable names (
example.com) into IP addresses. - Data is broken into packets that travel independently through routers, reassembled at the destination.
- HTTP/HTTPS is the application-layer protocol that browsers use to fetch web pages; HTTPS adds encryption via TLS.
The World Wide Web (Sir Tim Berners-Lee, 1989, at CERN) is the hypertext system layered on top of the Internet. The Internet and the Web are related but distinct: the Internet is the infrastructure; the Web is one application that runs on it.
Telecommunications
The same digital-communication principles underpin mobile telephony:
- 1G — analogue voice (1980s).
- 2G (GSM) — digital voice and SMS (1990s).
- 3G — data services, mobile internet (early 2000s).
- 4G LTE — broadband mobile, video (2010s).
- 5G — high-speed, low-latency, IoT-capable (now rolling out).
Fibre-optic cables carry pulses of light through ultra-thin glass strands, delivering the gigabit-per-second bandwidth that makes modern cloud services possible.