Part A: Computer foundations
Foundations of computing
Key takeaways
- A computer accepts data as input, processes it according to stored instructions, stores data and results, and produces information as output: the input-process-output cycle every computer follows.
- Data is raw facts with no context of their own; information is data processed, organised or given context so that it supports a decision.
- Booting runs from power-on through POST, the firmware finding a bootable device, the bootloader and the kernel loading drivers and services, up to the login screen; where it fails tells you what has failed.
- Computers are classified by size (supercomputer, mainframe, minicomputer, microcomputer), by type (digital, analog, hybrid) and by purpose (general-purpose or special-purpose).
- UEFI replaces BIOS, adding disks larger than 2 TB through GPT, faster boot and Secure Boot, which refuses a bootloader that is not digitally signed.
Every later paper in this diploma, from cabling a network to hardening a Windows server, assumes the same starting vocabulary a computer technician works from every day. This chapter sets that foundation: what a computer is, what happens between pressing the power button and seeing a login screen, how computers are classified, and where they are used.
Computing terms
The terms below are the ones an examiner expects a candidate to define precisely, not loosely. Each definition is followed by the way the term shows up in practice, because a technician is tested on recognising the concept in a scenario as often as on reciting it.
The distinction between data and information is the one most often examined in this group. A useful test: if you can act on it, it is information; if you first have to sort, count, compare or label it, it is still data. A sales system stores thousands of individual transaction records (data) and produces a monthly sales report (information).
Hardware and software depend on each other completely. Software runs only on hardware that meets its requirements (enough memory, a compatible processor), and hardware is useless without software to direct it. The operating system is the layer that sits between them, which is why the chapter on computer software gives it so much attention.
Computer booting process
Booting is the sequence a computer runs from power-on until it is ready for use. Understanding the sequence matters to a technician because where a boot fails tells you what has failed: no fan spin points to power, a beep code points to memory or the display adapter, a 'no bootable device' message points to the disk or its configuration, and a spinning logo that never finishes points to the operating system itself.
- Power-on: the power supply delivers stable voltages to the motherboard and the processor starts executing firmware from a chip on the board
- POST (power-on self-test): the firmware checks that the processor, memory, keyboard, display adapter and storage controllers are present and responding, reporting faults with on-screen messages or beep codes
- Firmware (BIOS or its modern replacement UEFI) locates a bootable device in the configured boot order: internal disk, USB drive, optical drive or network
- The bootloader on that device (Windows Boot Manager, GRUB on Linux) is loaded into memory and hands control to the operating system kernel
- The kernel initialises memory management, loads device drivers, starts system services and finally presents the login screen
- After login, the user's profile and startup programs load, and the computer is ready for use
Boot order in practice
Installing an operating system or running a diagnostic disk means changing the boot order in firmware setup so the USB or optical drive is checked before the internal disk. Forgetting to change it back afterwards is a common reason a computer later 'refuses to boot' when a stray USB stick is left plugged in.
Computer classification
Computers are classified three ways in this syllabus: by size (which is really by processing power and cost), by type (the kind of signal they process) and by purpose (how many different jobs they are built to do).
| Size class | Typical use | Users at once | Example |
|---|---|---|---|
| Supercomputer | Scientific simulation, weather modelling, cryptography | Thousands of parallel jobs | National research facilities |
| Mainframe | High-volume transaction processing, banking core systems | Thousands | A bank's core ledger |
| Minicomputer (mid-range server) | Departmental and organisational servers | Tens to hundreds | A hospital records server |
| Microcomputer | Personal productivity, workstations, mobile devices | One | Laptop, desktop, smartphone |
Computer application areas
A networking and systems administration career touches every sector, because every sector now runs on connected computers. The syllabus names five application areas; the examples below are chosen because they are the systems a Kenyan technician is likely to meet.
Classifying the computers in a county hospital
A county referral hospital asks a technician to list its computing equipment by class before a procurement review.
The hospital management information system runs on two rack servers in the ICT room serving 180 staff at once: mid-range servers (minicomputer class), general-purpose, digital.
Each ward and clinic has desktop PCs and a few laptops for clinicians: microcomputers, general-purpose, digital.
The laboratory analysers read blood samples through sensors and report results digitally: hybrid type (analog sensing, digital processing), special-purpose.
The infusion pumps and the X-ray console are embedded, single-task machines: special-purpose, digital.
The hospital has no mainframe or supercomputer; its heaviest workload, the records database, fits a mid-range server. Classifying this way tells the review where redundancy is needed (the two servers) and where a simple replacement policy is enough (the desktops).
Self-check
(a) Define a computer and name the four stages of the cycle every computer follows. (3 marks)
(b) Distinguish data from information, with one example of each drawn from a school. (3 marks)
(c) List the stages of the booting process in order, from power-on to the login screen. (5 marks)
(d) Classify the following by size, type and purpose: a bank's core transaction system; an ATM; a hospital patient monitor; a student's laptop. (4 marks)
(e) Name the five application areas of computers in this syllabus and give one Kenyan example for each. (5 marks)
Show worked answer
(a) A computer is an electronic device that accepts data, processes it according to stored instructions, stores data and results, and produces information as output. The cycle is input, process, store and output.
(b) Data is raw, unprocessed facts with no context, for example the individual marks 62, 71 and 48 entered for a class. Information is data processed into a meaningful form, for example the class average of 60.3% and the list of students below 50% who need extra support.
(c) Power-on and firmware start; POST checks processor, memory, display and storage; the firmware finds a bootable device in the boot order; the bootloader loads the operating system kernel; the kernel loads drivers and starts services; the login screen appears.
(d) Bank core system: mainframe, digital, general-purpose. ATM: microcomputer-class hardware, digital, special-purpose. Patient monitor: hybrid (analog sensing, digital processing), special-purpose. Student laptop: microcomputer, digital, general-purpose.
(e) Commerce (M-Pesa, supermarket point-of-sale); government (eCitizen, iTax); education (a university learning management system); entertainment (video streaming, gaming); science and research (KEMRI laboratory data systems, weather modelling).
Exam tip
The size-based classification (supercomputer, mainframe, mini, micro) is usually tested by description rather than name, so know what each is used for and how many users it serves, not just the order from largest to smallest. For the boot sequence, be ready to say what a failure at each stage looks like, since that is how the topic reappears in the troubleshooting paper.