Is a device or machine that takes in data, processes (manipulate) data to give out information OR

An electronic device that can execute instructions or commands to accept data (input), and process it to produce and store useful information (output).

DATA: consists of raw, unprocessed facts which when processed give information which is used for decision making Examples: Students particulars; first name, surname, age & sex. Also Hours worked.

Data may be in one of the following forms:

·         Alphabetic (A – Z)/text

·         Number (0 – 9)

·         Image/Graphic

·         Audio/Video

INFORMATION: Is a collection of facts organised in a way that gives additional information which is valuable for decision making Examples: wages for one’s weekly/monthly pay, pay checks and payrolls.

Characteristic of valuable information

·         Accurate

·         Timely

·         Complete

·         Relevant

PROCESSING; is converting data into information. The conversion of data to information include; calculation, comparison, summarizing, sorting etc.

INSTRUCTION; these are steps on how a computer can solve a problem. A group of instructions form a program. 


As a system, computer is a combination of six components

·         Hardware, e.g. mouse, monitor

·         Software; MS Office, DOS

·         Data/Information

·         Procedures

·         People

·         Communications 


·         Speed

·         Accuracy

·         Reliability

·         Large storage capacity

·         Low cost

·         Efficiency and Effectiveness

·         Automatic operations

o   Most important advantage of modern Electronic computer

o   Cary out a sequence of many different data processing operations without human intervention

o   Automation is possible through stored program 

Computer Applications

Applications are boundless

·         General businesses: Accounts receivable, Accounts Payable, inventory, personnel accounting, payroll etc.

·         Banking: Account reconciliation, instalment loan accounting, interest calculations, demand deposit accounting, trust services etc.

·         Government: income tax return verification, motor vehicle registration, budget analysis, tax billing, property rolls etc.

·         Military affairs: Weapon’s stock

·         Education: attendance and grade – card reports, computer – assisted instruction, research analysis, registration etc.

·         Personal use in homes



Five types (According to Size & Capacity): Generally, the larger the computer, the greater its processing power.

Microcontrollers (Tiny): The embedded computers; have specialized microprocessors. Installed in “smart” appliances and automobiles. Example, in microwave ovens the microcontroller stores data about time and temperature for cooking a particular food

Microcomputers-Personal computers:

·         Small computers; fits on desk; portable

·         Processor (CPU) built on a single silicon chip

·         Examples are: Desktop, laptops and pocket PCs


·         Like Desktop PCs but more powerful

·         For technical engineers and Scientists, Software development, scientific modeling

Minicomputers/mid-range computers:

·         Can be used as a single-user station

·         Mid way in cost ($000s) and capability

·         Has many processors

·         Size of an office desk

·         Higher speed than microcomputers

·         Users 100>user>1

·         Often used in Universities, Factories, or Research laboratories


Mainframes (large):

·         Oldest of the computer system

·         Size of Jeep

·         Operated by professional programmers and technicians in centrally managed departments within a large company

·         Handles millions of transactions in banks, insurance companies and airlines

·         Several peripherals are connected

·         Users 500>users>100


Supercomputers (Super large):

·         The fastest calculating device ever invented

·         Same peripheral devices as the mainframe

·         Used to model complex phenomena e.g. simulation of car crash into walls, exploration of oil, weather forecasting and sending astronauts


History of computers

·         Development of computers towards smaller size, more power & less expensive

·         Technological development of hardware and software termed Generations

·         Five generations of computer development


First generation (1944 – 1958):

·         Known as Vacuum tube age

·         Main memory: vacuum tubes (VT) for storage and processing data/information

·         VT Manually assembled

·         Size: Very large e.g. ENIAC, ~18,000VT, 30 tons, 1,500 sq. ft. of space

·         Power & Speed: slower than microcomputers, low storage capacity

·         Language: machine or assembly languages

·         Weaknesses: Heat, energy, VT breakdown


Second generation (1959 – 1963): Transistor age

·         Main memory: Magnetic cores

·         Storage devices: Removable magnetic disk packs

·         Transistors: Much smaller than VT, use less power, emitted less heat

·         Speed and power: faster than first machines

·         Language: COBOL, FORTRAN

·         Weaknesses: manually assembled, not heat resilient

·         Examples: IBM’s 1401, UNIVAC, BURROUGHS 


Third generation (1964 – 1970): The Integrated Circuit (IC) Age

·         Computer Memory: Expanded to 2MB of RAM memory

·         IC: 3 to 15 transistors on a single silicon chip for memory, logic and control of the computers system

·         Data storage: Magnetic disks (widely spread)

·         Speed and Power: Multiprogramming, Timesharing

·         Size & strengths: less expensive, smaller, high reliability, and lower power consumption, than transistor computers

·         Language: BASIC language (1965)

·         Software: Operating systems

·         Examples: IBMs


Fourth generation (1971 – 1990): The Microprocessor Age

·         Usage of LSI & VLSI circuits for memory, logic & control

·         INTEL: late 1970s, 100s – 1000s – 1000000 transistors on single small chip – Microprocessor

·         Computer memory: Increased

·         Software: Word perfect (word processing), Lotus (spreadsheet), dBase (database Management)

·         Microprocessor: Lead to miniaturisation of computers; creation of PCs, digital watches, Pocket calculators, copy machines etc.

·         Storage devices: Disks, Tapes, Exchangeable Magnetic disks etc.

·         Examples: The computers we use today


Fifth generation (1991-2000 and beyond): The age of Connectivity

·         Expanding (rapidly) internet, World Wide Web and intranets

·         Connectivity: Telecommuting (phones, fax & computers); Teleshopping (Cable TV shops); Email & Voice mail

·         Online information access: Database (electronic library, bank accounts);

Computer Hardware

Consists of all the machinery and equipment in a computer system

Divided according to the five operations of the computer: input, processing, output, storage and communication


·         For data entry into the computer

·         Translate data into a form the computer can process

·         Direct & Indirect Input Hardware

Direct input hardware: from the source document into the computer

·         To avoid copying/typing errors

·         Example: Pointing devices (e.g. mouse, digital video camera); scanning devices (e.g. bar code reader, fax machine), voice devices


Indirect Input hardware: prepared on a paper and entered into the computer by using keyboard

·         Example: keyboard, terminals

·         Read on the Key features of the keyboard, key-to-tape & key to disk systems



·         Used to display/give out the processed data (information)

·         Takes information from the computer to the user

·         Translates computer- processed information into a form that humans can understand i.e. from machine to human language

·         Two types of output;

o   Softcopy: data shown on a display screen or audio or voice form

o   Hardcopy: printed output


The softcopy output hardware:

·         Display screens

·         Cathode Ray Tubes: tubes used as a display screen in a computer or video display terminal

·         Flat Panel display: thinner, weigh less, less power

·         Voices output devices e.g. stereo & flat panel speakers


Hardcopy output hardware

·         Printers: prints symbols, characters & graphics on paper (impact Vs non impact) e.g. laser, ink-jet & thermal printers

·         Plotters: designed to produce high quality graphics e.g. drawing maps, architectural drawings

·         Multifunction printers: Printers that do more than print e.g. printing, scanning, copying & faxing

·         Microfilm devices: produces tiny images on rolls of microfilm/on sheets (cards) called microfiche; images 48 times smaller than printer output



The systems unit contains

·         The processing hardware (CPU) chip

·         The power supply (AC~DC)

·         Primary memory (RAM) chips

·         Motherboard

·         Expansion slots

·         Bus lines etc.



·         Microprocessor unit (MPU) for microcomputers

·         Work hand in hand with RAM

·         Most important part of a computer system

·         Two components:

o   ALU (arithmetic/logic unit)

o   Control unit (CU)


The Arithmetic/Logic unit (ALU)

·         Receives data from the memory of the computer

·         Carry out arithmetic operations such as addition, subtraction, division, and multiplication (computation)

·         Caries out logic operations like comparison e.g. true/false or yes/no

·         Returns results to a register then storage and/or determines the right action after


The control unit (CU):

·         Interprets instructions fed into the computer

·         Directs and controls the activities of the input devices, storage unit, ALU, and output devices as per instruction fed

·         Control the secondary/auxiliary storage units


RANDOM ACCESS MEMORY: Also known as primary memory

·         For intermediate storage until the process is proper;

o   Holds data for processing

o   Holds instructions

o   Holds information

·         Stored information lost when the power off

Four categories;

·         Conventional memory: for running operating system and application programs

·         Upper memory: store parts of operating system

·         Extended memory: memory above 1MB

·         Expanded memory: for expanding RAM


STORAGE HARDWARE: External and non-volatile and more permanent memory

Also known as secondary memory


·         Floppy disks (diskettes): Zip disks (100 MB), 2HD (1.44MB) etc

·         Hard disks: Internal hard disk (40GB), Hard disk packs (massive information)

·         Optical disks: the compact disks (CD)

o   CD-ROM: compact disk read only memory. For distribution of large databases, references & application software

o   CD-R: compact disk recordable, for permanently storing large amount of information

o   CD-RW: compact disks rewritable, erasable

o   DVD: digital versatile disks or digital video disks. Large capacity than normal CD (~4.7 GB)

·         Magnetic tapes

o   Magnetic tape streamers, for microcomputers, for back up of your hard disk, 10-20 GB

o   Magnetic tape reels, for minicomputers and mainframes


Computer Software

·         Are programs that control the operations of the computer

·         Are programs that make a computer useful

·         Program: group of instructions

·         Two kinds of computer software

o   Systems software

o   Application software


Application software: All those programs which facilitate a user to accomplish a given task.

·         Can perform useful work on general purpose tasks


Systems software: Enables the application software to interact with the computer & help computer manage its internal and external resources


Common features of software

Features of the keyboard

- Special purpose keys: used to enter, delete, and edit data and to execute commands e.g. Esc for escape, Ctrl, Del

- Function keys: labeled F1, F2 etc. used to execute commands specific to the software

The user interface: the user-controllable part of the software used for interaction or communication with the computer

The Graphical User Interface (GUI): allows to use graphics (images), menus & keystroke, to choose commands, start programs, see lists of files etc.

- Menus: a list of available commands presented on the screen e.g. menu bar, pull-down menu and pop-up menu

- Windows: a rectangular area that appears on the screen and displays information from a particular part of a program

- Icons: a picture used in GUI to represent a command, a program, a file or a task

- Buttons: on screen buttons activated (pushed) by mouse or other pointing devices

- Dialogue box: boxes on screen requiring user response 

Versions, releases, & compatibility

·         Developers enhance their products – new versions and releases

·         Versions: major upgrade in a software product; e.g. 1.0, 2.0, 3.0 etc. (higher number – more recent)

·         Releases: minor upgrade; e.g. 3.0 then 3.1, 3.11, 3.2

·         Compatible: documents created with earlier versions of software can be processed successfully on later versions OR new version of an applications program will run with the system software in place

Entertainment software: includes the video games (soccer), cards etc.

Home/Personal software: the interactive cookbooks, home repair, home decoration, gardening, travel planning etc.

Educational/Reference software: the Encyclopedia (Encarta), Almanacs, Math Blaster, maps, etc. 

Productivity software: word processing, spreadsheet, database & informational manager, financial, cyberspace etc.

Specialty software: desktop publishing, project management, drawing & painting, multimedia authoring

The Systems software:

·         Are programs that manage the operation of the computer

·         Concerns the manufacturer

·         Divided into three;

o   The operating systems (principal component), the commander-in-Chief

o   Utility programs, and

o   Language translators



·         Is a supervisor of all operations in a computer

·         Divided into two parts; control programs & service programs

·         Main functions are:

o   Provides for human-computer interaction (user interface), the controllable part of the operating system that allows you to interact with computer

o   Boots, or starts the computer operation

o   Schedule jobs (manage tasks)

o   Control input and output operations

o   Manages data and file storage

o   Assign different tasks to the CPU

o   Provides security and control


Examples of system software:

DOS (Disk Operating System)

·         This is a command-line; the operations needs commands; runs primarily on PC’s

·         Examples; MS-DOS 1.0 (1981) and other several upgrades; PC-DOS 7 (March 1995)

·         E.g. to format a Diskette, insert the diskette, then type after C:\>, ‘CD\DOS, FORMAT A:.’


WOS (Windows Operating System)

·         These are graphical user-interface (GUI) which consists of icons and use of mouse

·         Examples of WOS are: Windows 95, 98, XP, Vista, 7, 8, 8.1


NOS (Network Operating System)

·         These are special for networking, includes; UNIX (very powerful network and safe)

·         A multitasking operating system for multiple users

·         Has built-in networking capability and versions which can run in all types of computers

o   LINUX (a form of UNIX; modified UNIX)

o   Windows NT

·         A product from MS

·         A multitasking, multi-user, multiprocessing network operating system with a graphical user interface

o   Windows 2000


UTILITY PROGRAMS: Special programs that (1) enhance existing functions and/or (2) provide services not provided by other programs

·         Backup: make duplicate of every file on your hard disk, diskettes, flash etc

·         Data recovery: used to resurrect accidentally deleted information e.g. “undelete or undo”

·         File defragmenter

·         Virus protection, the antivirus programs



A software that translates a program such as word, written by a programmer in a language such as C, into a machine language (0s and 1s)



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