Difficulty: Beginner | Prerequisites: None
This topic is the starting point for any computer science course. It covers what a computer is, the difference between hardware and software, and the broad categories of computers you will encounter. If you have never studied computing before, this is where you begin. Everything else in the course, from programming to networking, builds on these definitions and distinctions. You should be comfortable with these fundamentals before moving on to more specific hardware or software topics.
A computer is an electronic device that stores, retrieves and processes data using hardware (physical parts) and software (instructions). Computers range from large mainframes used by banks and corporations down to personal computers used at home and in offices. Understanding the hardware/software distinction is the foundation for every other topic in this course.
Computer
An electronic device that stores, retrieves and processes data, and can be programmed with instructions. It is composed of hardware and software and can exist in a variety of sizes and configurations.
In simple terms, any programmable machine that takes in data, does something with it, and gives you a result.
Hardware
The physical components of a computer: the system unit, mouse, keyboard, monitor, and so on. Anything you can touch.
Think of it as the body of the computer.
Software
The instructions that make the computer work. Software is stored on disk (hard disk, CD-ROM, DVD) and loaded into RAM when needed.
Think of it as the mind of the computer, the set of rules telling the hardware what to do.
Mainframe computer
A very powerful, very expensive computer used by large organisations such as banks to control entire business operations.
In simple terms, the big central machine that runs everything for a large company.
Personal computer (PC)
A relatively cheap, easy-to-use computer designed for individual users. Can operate as a standalone machine or be connected to a network.
In simple terms, the computer on your desk or in your bag.
An electronic device that stores, retrieves and processes data
Can be programmed with instructions
Composed of two fundamental parts: hardware and software
Exists in many sizes, from room-filling mainframes to pocket-sized devices
Hardware refers to every physical component: system unit, mouse, keyboard, monitor, printer, cables
If you can physically touch it, it is hardware
Software refers to the instructions (programs) that tell the hardware what to do
Stored on disk (hard disk, CD-ROM, DVD, floppy disk)
Loaded from disk into RAM when the computer needs to run it
Without software, hardware is an expensive paperweight
Mainframe and minicomputers
Very powerful, used by large organisations (banks, governments, airlines)
Control entire business operations centrally
Very expensive to purchase and maintain
Personal computers (PCs)
Comparatively cheap and designed for individual use
Can work standalone or be connected to a network
May also connect to a mainframe within a large company
The hardware/software distinction matters every time you troubleshoot a problem: a flickering screen is a hardware issue, a crashing program is a software issue. Knowing which type of computer fits a task is how organisations decide whether to invest in a mainframe (for centralised banking systems, airline reservations) or deploy personal computers (for office productivity, remote working).
Students often think "hardware" means only the parts inside the case. It includes every physical component: the monitor, keyboard, mouse, printer and cables are all hardware.
Students sometimes confuse the operating system with application software. The operating system is the foundational layer that starts when you power on; applications run on top of it.
A mainframe is not simply "a big PC." Mainframes are architecturally different, designed for massive concurrent workloads and high reliability. A PC scaled up in size is still a PC.
"More RAM" and "more storage" are often conflated. RAM is temporary working memory (volatile, lost when powered off). Storage (hard disk, SSD) is permanent. They serve different roles.
⚠️ Be able to define "computer" in one sentence and name its two core components (hardware and software).
⚠️ Know examples of hardware vs software and be able to classify a given item as one or the other.
⚠️ Understand the distinction between mainframe/minicomputers and personal computers, including typical use cases for each.
True or false: Software is any physical component of a computer. (False, software is the instructions/programs.)
Fill in the blank: A ______ is a very powerful computer used by large organisations to control entire business operations. (mainframe)
True or false: RAM retains its contents when you switch off the computer. (False, RAM is volatile.)
Fill in the blank: The two fundamental parts of any computer are ______ and ______. (hardware, software)
True or false: A personal computer cannot be connected to a network. (False, PCs can work standalone or networked.)
Q: Define what a computer is in your own words.
A: A computer is an electronic device that stores, retrieves and processes data according to a set of programmed instructions. It consists of hardware (physical parts) and software (programs).
Q: Give three examples of hardware and three examples of software.
A: Hardware: keyboard, monitor, hard disk drive. Software: Microsoft Word (word processor), Windows (operating system), Microsoft Excel (spreadsheet).
Q: What is the key difference between a mainframe computer and a personal computer?
A: A mainframe is a very powerful, expensive computer designed for large organisations to handle massive centralised workloads. A personal computer is cheaper, designed for individual use, and can operate standalone or on a network.
Q: Explain the relationship between hardware and software.
A: Hardware provides the physical platform (processor, memory, storage, input/output devices). Software provides the instructions that tell the hardware what to do. Neither is useful without the other.
This material connects directly to the Hardware Components topic (Part 2 of these notes), where each type of input device, output device, storage device and memory is covered in detail. It also underpins the Software, Networks and Security topic (Part 3), since understanding what software is leads into the distinction between operating systems and application software, and knowing what a network-connected PC is leads into LANs and WANs.
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