Computer Fundamentals and Hardware
Foundations
Computer Fundamentals and Hardware
Syllabus tag: KASNEB CPA | Foundation Level | CA16 Information Communication Technology | Topic 1 Computer Fundamentals and Hardware
Lesson objectives
By the end of this topic, you will be able to:
- Describe the components of a computer system
- Explain the function of the CPU and its parts
- Distinguish primary from secondary storage
- Classify input, output and storage devices
- Explain the units in which storage is measured
Why this matters
An accountant does not build computers, but does authorise the purchase of them, assess whether a system can carry the workload, and understand why a process that ran overnight now takes four hours.
The four functions
Every computer system performs: input, processing, storage and output. Every device belongs to one of them, and the classification is a standard examination question.
The central processing unit
Three parts:
- Control unit — fetches, decodes and directs the execution of instructions
- Arithmetic and logic unit (ALU) — performs calculations and comparisons
- Registers — very small, very fast storage holding the data currently being worked on
Clock speed, measured in gigahertz, indicates cycles per second. It is not a complete measure of performance: the number of cores, the cache size and the speed of memory all matter. A higher clock speed alone does not guarantee a faster machine.
Primary storage
| RAM | ROM | |
|---|---|---|
| Purpose | Holds data and programs in current use | Holds start-up instructions |
| Writable | Yes | Effectively no |
| Volatile | Yes — contents lost on power off | No |
RAM is volatile, and that single fact explains a great deal. It is why unsaved work vanishes in a power cut, why a system with too little RAM slows sharply — it resorts to swapping data to disk, which is far slower — and why adding RAM often improves performance more than a faster processor would.
Cache is a small amount of very fast memory between the CPU and RAM, holding the data most likely to be needed next.
Secondary storage
Non-volatile: contents survive when power is removed.
| Device | Characteristics |
|---|---|
| Hard disk drive (HDD) | Magnetic, high capacity, cheaper, moving parts |
| Solid state drive (SSD) | Flash memory, much faster, no moving parts, dearer |
| Optical (CD, DVD) | Removable, low capacity, largely superseded |
| Magnetic tape | Very high capacity, sequential access, used for archiving |
| Flash drives and memory cards | Portable, convenient, easily lost |
| Cloud storage | Off-site, accessible anywhere, needs a connection |
Magnetic tape survives for one reason: sequential access is no disadvantage when restoring a whole backup, and the cost per terabyte remains the lowest available. Its weakness — you cannot jump to a record — does not matter for archiving.
Units of storage
| Unit | Approximate size |
|---|---|
| Bit | A single 0 or 1 |
| Byte | 8 bits — one character |
| Kilobyte (KB) | 1,024 bytes |
| Megabyte (MB) | 1,024 KB |
| Gigabyte (GB) | 1,024 MB |
| Terabyte (TB) | 1,024 GB |
Each step is 1,024 rather than 1,000, because storage is counted in powers of two: 2¹⁰ = 1,024.
Input and output devices
Input: keyboard, mouse, scanner, barcode reader, touch screen, microphone, biometric reader.
Two worth knowing by name:
- OCR (optical character recognition) converts printed or written text into editable data
- MICR (magnetic ink character recognition) reads the characters at the foot of a cheque, and is used because magnetic ink is hard to forge and readable even when the cheque is marked
Output: monitor, printer, plotter, speakers.
Some devices do both — a touch screen, a network card, and any storage device, which receives and supplies data.
:::checkpoint A payroll system has begun taking four hours to run a process that previously took forty minutes, with no change in the number of employees. Suggest two hardware explanations, and say which you would investigate first. :::
Classifying computers
Supercomputers — scientific modelling and weather forecasting. Mainframes — large organisations processing very high transaction volumes; banks still run core systems on them. Servers — provide services to other machines on a network. Personal computers and laptops — individual use. Tablets and smartphones — mobile, touch-based. Embedded systems — computers inside other devices, from vehicles to point-of-sale terminals.
The mainframe persists because reliability and transaction throughput matter more than raw speed in a banking system. It is a case where the older technology remains the right answer.
:::checkpoint A company is choosing between hard disk and solid state drives for its accounting server. Set out the trade-off, and say which consideration should decide it. :::