Introduction to Computing Systems cheat sheet

Key terms

Computer

An electronic device that accepts data as input, processes it according to a stored set of instructions (a program), stores data and results, and produces information as output. The four verbs, input, process, store and output, are the input-process-output cycle every computer follows, whether it is a smartphone or a data-centre server.

Input

Data or instructions fed into a computer for processing, and by extension the devices that do the feeding: a keyboard, a mouse, a scanner, a microphone, a barcode reader at a supermarket till. Input is anything that crosses from the outside world into the machine.

Output

The processed result a computer produces and presents to the user, and the devices that present it: a monitor showing a document, a printer producing a report, a speaker playing audio, a network card sending a file to another machine. Output is anything that leaves the machine for the outside world.

Hardware

The physical, tangible components of a computer system: the processor, memory chips, disks, motherboard, power supply, cables and every peripheral. Hardware can be touched, and it can fail physically, which is why hardware faults have symptoms such as heat, noise or no power at all.

Software

The programs and instructions that tell the hardware what to do: the operating system, device drivers, utilities and application programs. Software cannot be touched; it is stored as data on a disk and loaded into memory to run. A machine with perfect hardware and no software does nothing.

Data

Raw, unprocessed facts and figures with no context of their own: the number 37, the word 'Nakuru', a stream of temperature readings. On its own a data item answers no question.

Information

Data that has been processed, organised or given context so that it becomes meaningful and useful: '37 students registered from Nakuru this term' is information built from the same raw items. Information supports a decision; data merely records.

Cold boot and warm boot

A cold boot starts from a powered-off state and runs the full POST. A warm boot (restart) reloads the operating system without cutting power and skips part of the hardware check, which is why a stubborn hardware fault sometimes clears only after a full shutdown.

BIOS versus UEFI

BIOS is the older firmware standard: text-based setup, 16-bit code, disks limited to 2 TB under the MBR partition scheme. UEFI is its replacement: graphical setup, support for disks larger than 2 TB through GPT partitioning, faster boot, and Secure Boot, which refuses to load a bootloader that is not digitally signed, blocking boot-sector malware.

Size

From largest to smallest: supercomputer, mainframe, minicomputer (today called a mid-range server) and microcomputer (a personal computer, laptop, tablet or smartphone). Size here tracks processing power, memory, price and the number of simultaneous users, not physical dimensions alone.

Type

Digital computers process discrete values (binary 0 and 1) and are the vast majority of modern machines. Analog computers process continuous physical signals such as voltage or pressure and are found in older instrumentation and some control systems. Hybrid computers combine both, taking analog measurements and processing them digitally, as in hospital monitoring equipment.

purpose

A general-purpose computer runs many different kinds of program (a PC, a server). A special-purpose computer is built and programmed for one task and does it very well: a network router, an ATM, an embedded controller in a washing machine, a point-of-sale terminal.

Commerce

Point-of-sale terminals, mobile money platforms such as M-Pesa, online shopping, stock control and accounting systems. The technician's concern is uptime: a till that cannot reach its server stops the business.

Government

Public records, eCitizen services, tax filing through iTax, county revenue systems and secure networks between agencies. These systems carry personal data, so access control and audit trails matter as much as availability.

Education

Campus networks, learning management systems, online examinations, digital libraries and computer laboratories. Peak loads (exam day, registration week) and shared machines with many users shape the support workload.

Entertainment

Streaming video and music, online gaming, digital broadcasting and content production. These are bandwidth-hungry applications, and their users are the least tolerant of latency.

Science and research

Laboratory instruments, research data storage, modelling and simulation, and data centres hosting large datasets. Data integrity and long-term storage dominate here.