GHS/Computer Studies/Computer hardware

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These are physical components of a computer that can be seen and touched e.g mouse, keyboard etc Hardware can further be categorised into input , output, system unit, storage and communication devices.

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Other definitions
  1. Peripheral devices: These are devices that are connected to the computer's system unit like keyboard, printer etc. It can also refer to devices connected to the computer. for example mouse, scanner, digital camera etc
  2. Input devices: These help the user to enter data into the computer for example digital camera, keyboard, scanner, mouse etc
  3. Output devices: Devices that give out information after processing e.g monitor, printer,
  4. Memory: Refers to chips that store data for fast access by the central processing unit in case its needed. for example RAM and ROM

OR it can also refer to

Input devices

Any thing that is used to enter data into the computer e.g

  • digital camera
  • mouse
  • joystick etc

more details

Output devices

These are devices that give out information after processing examples include monitor(Video display unit), printer, plotter, speakers etc. These devices are in two types

  • Softcopy output devices: Softcopy refers to the intangible output displayed on screen and other output devices like speakers.
  • Hardcopy output devices: A hard copy is a tangible output produced on papers for example by a printer

1. Monitor

It is the most common output that looks like a television screen, used to display information on screen thus helping the user to monitor operations carried out by the computer. There two main types of monitors namely:-

  • Cathode ray tube
  • Flat panel display

Advantages of a monitor

  • Relatively cheap.
  • Information is displayed very fast.
  • No paper is required for output.


  • Information on a monitor screen it temporary therefore can be lost when power i s off.
  • Cannot be used by visually impaired persons.
  • Spoil eyes if used for many hours without breaks.

Cathode ray tube(CRT)

This monitor has a vaccum tube that emits light. Its screen has a convex shape(curved outwards)allowing the user to view data entered into the computer from different angles. The principal elements of a CRT are:- An electron gun used to fire electron beams inside the screen. A yoke is a cylinder infront of an electron gun that controls magnetic fields. Shadow mask is a shield with holes used to prevent diversion of a beam and ensures that a small portion of that beam reaches the screen. phosphor creates display seen on screen.


  • Can be viewed from a wide angle this is because of the convex shape of the screen.
  • Produce faster and rich color.
  • Cheaper than LCD monitors.


  • They are large and bulky because of the different components used to make them and there sizes. Therefore not portable.
  • Consume alot of power therefore cannot be run on batteries like laptops and other portable computers.
  • Its screen can easily be damaged because of its shape.


  • Colour monitor:

This type of monitor can display text and graphics in more than one colour even in millions. But this will depend on the amount of memory installed on the video adapter. Therefore for any monitor to display colour it must have a video card or video adapter.

Video cards are in different types these include; 1. CGA (Colour graphics adapter):This has a monitor resolution of 320 * 200 pixels and a capability of dispalying 16 different colours though not many colours at a time.

2. EGA (Enhanced graphics adapter): It has the capability of dispalying 64 colours though not many at a time and its resolution is 640 * 340 pixels. 3. VGA (Video graphics array adapter): Has a resolution of 640 * 480 pixels, with the capability of dispalying 260,000 colours though it can display only 256 colours at a time. 4. SVGA(Super Video graphics array adapter): This card can display more than 16 million colours and its resolution is 1280 X 1024 pixels. 5. XGA (Extended graphics array): XGA provides higher resolution and more colors than the VGA and SVGA cards at the time though it can only be used in IBM machines.

The information displayed by colour monitors is very attractive however some the disadvantages of colours is reducing the speed at which the screen can display information and also occupying alot of memory space in ones computer.

  • Monochrome monitors: This type monitor has the capability of displaying only a single colour and have good quality images because of the gray scaling. Thety can be used by business people who are more concerned about the cost incured than colour.

Flat panel display

Its a thin display screen that is used in most portable computers. These displays are in three common types 1. Liquid crystal display(LCD) 2. Gas plasma display 3. Electroluminescent display.


These have liquid crystals that reflect light falling on them from the environment therefore they do not emit their own light. LCD technology are used in calculators, digital cameras and laptops etc


  • LCD's use less power than other monitors therefore can be used in watches etc
  • They are cheap
  • Small in size and more durable than plasma displays.


  • Have images of very little contrast
  • The viewing angle is small because of the flat nature of the screen.


These emit light when electronically charged. They are therefore clear and easier to read, they use too much power therefore not suitable for battery powered laptops, smaller in size than CRT. The image resolution is high etc.


These were the first machines produced by IBM, they were huge and could display up to 4 pages at once. They have very good images( normally in orange with a black background) compared to CRT's and LCD's. Its viewing angle is excellent than the LCD's. There are some laptops that use plasma display like ericsson portable PC, toshiba 3100 etc


  • They use alot of power than LCD's.
  • It is an expensive technology.
  • Display information only in a single colour ie reddish orange.
  • larger than LCD's for example commonly ranging from 42 to 63 inches compared to LCD's which range between 15 to 32 inches. They could even be larger.


Resolution refers to the clarity of image on screen or can be defined as the number of pixels that are used to draw an image on screen. images are displayed on screen using dots or pixels. Therefore the resolution of an image on screen is directly related the number of pixels the monitor can display and the distance between each dot. Example:1. Given 800 horizontal pixels and 600 vertical pixels, calculate the monitor resolution.

Monitor resolution = Vertical resolution * horizontal resolution

Vertical resolution = No of pixels per character box vertically * No of lines of text.

Horizontal resolution = No of pixels per character box horizontally * No of characters displayed per line.

2. Given a number of pixels per character box as 9 and number of characters that can be displayed per line as 80, Calculate the horizontal resolution.

NB: Dot pitch: Refers to the distance between pixels of the same colour in millimeters. Therefore the smaller the distance the sharper (clear) the image will be. Refresh rate: refers to number of times per second in which a display is illuminated or lit up Response time: Amount of time a pixel takes to change from black to white and vice versa. which is measured in milliseconds.

2. Printer

A printer is an output device used to print characters, symbols and some times graphics on paper. An output device used to give out information on paper. The printed information is in form of hardcopy and permanently exists on paper.


There number of factors that determine the classification of printers ie; According to the print mechanism and amount of information a printer can write at a particular time. The speed of a printer is determined by the number of pages it can print per minute(PPM) and its resolution is determined by DPI(dots per inche); the higher the number of dots per inche, the better the resolution of that printer or clarity of its output.

Advantages of printers.

  • They give out permanent output.


  • Paper is required in order to get the output.
  • Its not as fast as the monitor in giving output.

There two main categories of printers namely;

  • Impact printers.
  • Non impact printers.


These are printers that transfer image or text on paper by the print mechanism stricking the paper, ribbon and character together. These printers are generally noisy and produce rough work (letter quality print) for example on cloth, paper, transparencies etc. For example they can be used to create labels on envelops. Impact printers are in different types namely;

  • Dot matrix printers:
  • Daisy wheel printer:


These produce hardcopy using the stricking mechanism ie the print head pins strike the inked ribbon together with the paper to form characters and the combination of small dots printed closely together forms a character. It should be noted that the more the number of pins on the print head of this printer, the better the quality of output. Dot matrix printers are used in areas with intensive transaction processing which requires alot of printing eg in large organizations to print invoices, bills, purchasing order for clients etc


  • They can survive a dusty environment with high temperatures.
  • They can print on continous paper( multipart forms). This does not require individual sheets to be inserted into the printer and its also useful to record related data in a sequence.
  • Less expensive for example in a home where quality is not a concern and also have the lowest cost per page used.
  • Generate less noise than daisy wheel printers.


  • Slower than
  • noisy because of the stricking mechanism therefore not good for use in a quite environment.
  • They have the lowest print quality than laser and inkjet.However they are still used today in business to print multipart forms.


This prints by rotating the print wheel until the right character is aimed at the paper. They are slower and more expensive than dot matrix printers, cannot print on graphics, produce loud sound and cannot change fonts unless the print head replaced. It offers most of the advantages of a dot matrix with better quality and not easily damaged.


Printers that do not strike characters against ribbon or paper when they print. Common examples include;


It uses a technology similar that of a photocopying machine to transfer image or text on paper. This is by passing a laser beam of light back and forth over a rotating drum. A point on drum touched by the beam is charged and attracts toner which is then transfered and fused on paper by heat or pressure to create text or images. They use powdered ink to generate a desired output on paper.


  • Quite and fast for example in four minutes it can print between four to thirty pages of text.
  • Produce highest quality output both text and graphics ie with a resolution ranging from 600dpi to 1200dpi which is better than the inkjets.
  • Low cost per page if its in black and white and huge amount of output compared to inkjets.
  • Can print on different papers eg envelops, cards etc which may not be the case with inkjets.
  • They are cheap to produce and the cost of a colour printer is fairly low.

These print by spraying tiny drops of liquid ink on the paper using heat or pressure. Its print head contains nozzles with small holes through which ink is propelled. inkjets use colour catridge of mangenta, yellow and cyan ink to create colour tones. but black catridge can also be used for monochrome output.

Inkjet manufactures are aiming at improving these printers to print on most paper types.


  • Less expensive than laser printers.
  • Quite because they do not use a striking mechanism.
  • Produce good quality output of both text and graphics and are the best option for producing colour output therefore more desirable by home users and business people than the laser printers.
  • Documents printed with liquid ink are difficult to alter than those printed with toner or solid ink. this is because the toner does not penetrate below the paper surface.


  • Clogged inkjets ie the nozzles can be blocked with ink over time.
  • Maintainance cost is high in terms of cartridge required therefore more expensive than laser printers.Also special paper is needed to produce high quality output and the cost per page of inkjets is far more higher than all other printers.
  • They are slower than laser printers therefore not suitable for large volumes of work.
  • Ink may smear when printed on ordinary paper. however this problem has been reduced with the development of new ink compositions.


Printers that transfer characters onto a piece of paper using hot pins which presses a special ribbon to print on a chemically treated paper or paper sensitive to temperature. they are widely used in battery powered devices like calculators etc

The commercial application of thermal printers are the filling station pumps(ie sell fuel and lubricants for motor vechilces eg gas station, service station,petro station garages etc) ,information kiosks ( where free information in form of maps and other literature is offered) and point os sale systems (locations where transactions are made eg in hotel, supermarket, restaurant stadiums etc) Advantages:

  • They are faster and quiter than dot matrix printers.

Exercise: Qn. Using the google search engine, write down other advantages and disadvantages of a thermal printer.

3. Plotter

A plotter is a graphics printer and they are in two main types; ie the pen plotters and electrostatic plotter(produce good images but with quality not better than pen plotters) Pen plotters print by moving a pen (coloured pens) across the surface of a piece of paper to draw lines and diagrams. This means that they are restricted to line art, rather than raster graphics as with other printers. They can draw complex line art, including text, but do so very slowly because of the mechanical movement of the pens. Pen Plotters are incapable of creating a solid region of color; but can hatch an area by drawing a number of close, regular lines. Plotters were the fastest way to produce color high-resolution vector-based artwork, or very large drawings efficiently when the computers processing power was still low. They are also used by engineers to draw building plans, scientists can make different machine parts, circuit boards etc.


  • Produce larger printouts than standard printers.


  • Slow and relatively expensive compared to printers.
  • Cannot print photograghic images.
  • Only make solid blocks of colour using lines that are close to each other.

4. speakers

These are audio output devices that give out any kind of sound like spoken words, music etc. Some speakers can be inbuilt(ie inside the system unit) while others are external(ie connected to port of the sound card that works with sound , voice and music software). A sound card allows output of sound through speakers and in case a user needs to enter data into the computer in form of spoken words they can use the same. They are analog devices therefore the digital sound has to be converted into analog.


  • Can be used by the blind or any individual with sight problems to enter data into the computer in form of spoken words.
  • Output can be shared by more than one person.
  • They are cheap and produce high quality sound.


  • Not suitable for use in a quite environment eg office, class etc

5. Headset

Used by an individual

6. Projector

Its used to display information from the computer onto a larger screen to be seen by a bigger group of people. for example they can be used in workshops , meetings , classes for presentation. projectors are in different types and display inmages of varrying quality.

Storage devices

These are devices that keep data for future use examples include memory stick, hard disk, floppy disk, compact disk, DVD( digital versatile disk) etc. Storage devices are in two different types namely:- The temporary(primary storage) and permanent storage devices (secondary storage).

Temporary storage devices

They are used to keep data and programs for a short period of time. This is also referred to as RAM or volatile memory.

Permanent storage devices

These store data and programs permanently for future use for example CD-ROMS, floppy discs, hard disk, flash etc. The permanent storage locations for data and information other than the main memory are also called secondary or auxiliary storage devices or mass storage devices. They can be carried around (removable storage devices eg floppy , flash, zip and jazz disks, magnetic tapes, some portable hard disks etc) while others are housed inside the system unit like the hard disk.

The most common storage devices on microcomputers include:
  1. Tapes
  2. Fixed disk or hard disk
  3. Zip drives
  4. Punched cards
  5. Floppy disk
  6. CD-ROM

Secondary storage devices are further classified into two groups according to the way they record data on a media for example; 1. Magnetic storage devices. 2. Optical storage devices.

MAGNETIC STORAGE DEVICES. These are used to store data or information on a magnetically coated surface. The information is written or accessed on a media using the read and write head and its non-volatile. examples of magnetic storage devices include magnetic tapes Floppy disk Hard disk

Magnetic tape It is a ribbon of plastic like material coated with a magnetic surface onto which data is recorded in form of magnetic particles. To read data from the tape, it must be inserted in a tape drive hence the read and write head performs its operations. Tapes are still used in large organizations to backup data because some have much more storage capacity than CD's and DVD's for example ranging from 10GB to more than 300GB.

Disadvantages of magnetic tapes

  1. Data access is slow due to linear storage. Therefore used to store data that is not accessed so often.
  2. Bulky hence fill up alot of space.
  3. The tape is worn out due to winding and unwinding leading to data loss.
  4. Its data cannot be altered.


  1. They are portable
  2. Good storage capacity e.g 20-500MB

Floppy disk

A floppy is a thin circular plastic material with a magnetically coated surface on which data is recorded using the read/write head. Floppies are in different sizes but the commonly used disk has the capacity of 1.44mb (3 1/2 inch)


  1. Data access is faster than tapes this is because of the circular shape.
  2. They are portable
  3. Cheap and easily available

4.It has a write protect notch meaning data will not be modified by unauthorized users.


  1. Exposing of magnetic fields of the media can lead to loss of data.
  2. Data life is unreliable especially if the floppy is not handled with care.

3. Cannot hold alot of information like other storage devices eg flash disc, CD's etc 4.Access time of locating an item is slow.


  1. It should be kept away from magnetic fields to avoid loss of data
  2. Should not be removed from the drive when the read or write operations are taking place.
  3. Should not be placed in the drive while the computer is turned on or off.
  4. Do not expose it to dust aor heat
  5. Do not touch the surface of a disk

Magneto-optical disk

They use both laser and magnetic fields to backup large amounts of data.

Hard disk(drive)

A hard disk drive (HDD), commonly referred to as a hard drive, hard disk, or fixed disk drive, is a non-volatile storage device which stores data on rapidly rotating platters with magnetic surfaces. They provide a very fast way of retrieving data. It should be noted that hard disks are housed inside the system unit (fixed hard disks) while others are removable. The hard disk store large amounts of data for example programs that are used by the computer like the operating system and others, it also organizes files for easy access.

NB:A platter is a round magnetic plate with two read/write heads on each of its sides on which data is stored. A hard disk can have more than one of these platters and the more platters a disk has,the more its storage capacity will be.


1. Format the hard disk by removing all the data that is on it. Its the process of preparing the disk to read and write data. But this is not mandatory it can only be done if one needs a clean hard disk without viruses, a hard disk that is to be sold without any programs etc. During the formatting process, the operating system checks the reliability of the disk, it marks the bad sectors ie those scratched and damaged and erases unnecessary information.

2. The disk is partitioned by creating tracks and sectors in order to save data in a more organized way. The importance of creating partitions on a hard disk is that every partition is independent from the other partitions meaning that Incase files or programs in one partition are corrupted, then files in other partitions are still safe. This is another reason why a hard disk should be partitioned before saving data on it.

The concentric circles on each platter are called tracks and the division of these tracks into small units are called sectors. While a collection of different of tracks is refered to as a cylinder.

A hard disk can have one or more partitions defined as C:/ drive, D:/ drive and so on. And the flow of data or information to and from the hard disk will be managed by the hard disk controller(HDC)

3. Save data on the disk.

Please leave space for the diagram: to be drawn in class


  1. Data is secure because some hard disks are not portable. though there new hard disks that are portable.
  2. Stores data for a long period of time
  3. Store large amounts of data more 20MB-6GB more than floppies and other storage medium
  4. Data access on a hard disk is faster than the floppy.


  1. Can be attacked by viruses hence data loss. This is because files or programs in some sectors infected will be corrupted. if a file is corrupted the file loses its data, some files cannot open and if its a program like the operating system the computer cannot be used.
  2. Some are not portable making data less secure eg incase a computer is stolen all data will be lost.
  3. Head crash of the hard disk due to dust leading to data loss.
  4. Removable hard disks are expensive.

Zip disk

They are like floppy disks though larger, thicker and have more storage capacity than floppies. eg storage capacity ranges from about 250MB to 750 MB of data. To read or write data on the disc it should be inserted into the drive which is external and portable.

Jazz disk

They are small portable disks with storage capacity of 1 to 2GB of data. They also use a portable drive in which a disk is inserted in order to read or write data on it.

flash disk

Flash disk: These are devices that are portable, hold more data and are more durable than floppy and zip disks. To store or retrieve data on a flash, its plugged into a computer's USB port and it will be registered as a removable device. some flash disks have a storage capacity of 1 0r 2GB and some upto about 64GB.


  • Portable because of the small size it helps the use to have to data whenever its needed.
  • Store much more data than floppy disks.


  • Unathorized company employees can smuggle confidential data of the company or organization without being detected.
  • It can easily be lost because of the small size leading to data loss.
  • Incase its infected with a virus, it can easily infect the entire network by plugging it in different USB ports.

Memory sticks

They are like cards and are inserted in a card reader which is connected to the computer or digital camera. They are used mainly in digital cameras and personal digital assitants(PDA)to store data.


Optical disks store data or programs using a laser beam of light to store and read data from the disc. Some of these discs are read only while others are read and write. for example compact disks(CD), super disk, DVD(digital versatile disk), optical card and optical tape flash disk etc. They help to store data permanently and its data life is long as long as the CD is kept well to avoid scratches.

NB: To record data on a Cd one needs a CD writer. Examples of optical storage devices include;

1. CD(compact disk): These are used to store information that requires alot of space like video clips, software, sound etc. CD's are in different types for example CD-ROM, CD-R, CD-RW etc.

CD-ROM(Compact Disk Read Only Memory): These are used to store and play audio, video, graphics images and digital data and software programs. therefore can be used to store and retrieve digital data. A single Cd has the capability of storing 600 to 700mb of data,which is equivalent to about 450 floppies of 3 1/2 inche. However it should be noted that once data has been written on a CD-ROM , it cannot be altered or new data added to the media. It is also slow in accessing compared to hard disk.

CD-R(Compact disk recordable)These are initially blank Cd's that can be used to record data and software only once using a CD- writer or Cd drive. The process of writing data on a Cd is called CD burning. In order to write data on a CD-R a software is needed for example "Nero burning ROM" is a software used in most personal computers. While windows operating system has it built in software for writting data on a CD-R. The disadvantage of CD-R is that information can be written only once and cannot be overwritten or erased. However data can be stored in other parts of the Cd that are not yet written into to make it full. CD-R's are also more expensive than CD-ROM.

NB: The rate of data transfer from the Cd to the computer is measured in Mbps(mega bits per second).

CD-RW(Compact disk rewrittable)these are disks that allow a user to record data, erase and rewrite new information more than once. Therefore such data cannot be altered.

Note: Cd's that allow the user to record data only once but can read it as many times as they can is refered to as WORM( wite once read many)e.g Cd-R and CD-ROM

Advantages of Compact disks

  • portable because of the small size
  • data remains intact without being altered for some Cd's
  • data access is fast depending on the the Cd drive
  • store large amounts of data like sound, videos and graphics


  • A small scratch on a Cd leads to loss of some data

2. DVD( digital versatile disk or Digital video disc) These storage medias are replacing Cd's due to the high storage capacity. for example a single DVD stores data of 26 Cds They store 15 times much more information than CD's and are about 20 times much more faster than CD's in data access. some DVD's can store a four hour movie on one side only while others have even much more storage as they can keep data on both sides. DVD's are in different types eg DVD-ROM, DVD-RAM, DVD-RW, DVD-R,DVD+R, DVD+RW. DVD-R,DVD+R can record data only once while DVD-RAM, DVD-RW, DVD+RW can be written as many times as the user wants.


  • Its easy to share any information stored on it.
  • Offer high quality sound and video pictures than CD's.
  • Portable because the size.
  • Data life is long than magnetic tapes especially if handled with care

DVD-ROM (DVD Read Only Memory): These can store interactive games, photographs etc.

VCD(video compact disk): Has high storage capacity of about 650 to 700MB. they are least expesive devices

SD(secure digital)cards:

Communication devices

These are devices that help computers to communicate or share data and information. Examples include network interface card, repeater, router, hub etc

1. Modem(Modulator and Demodulator): It is used to transmit data from digital data from the computer to analog data such that it can be transmitted along a telephone line. In the same way it converts data from analog to digital because computer data is in digital form. A good modem should be able to transmit one page per second.

2. (NIC)Network interface card or Network adapter: It enables computers that are linked together to communicate using a cable. The cable connects the NIC to a router. This enable sharing of network reources like printers etc, information, files and programs.

3. Cables: These are cables on the circuit board of the motherboard that enable communication between the devices and the CPU. OR cables used to connect communication devices to form a network. e.g coaxial, ethernet and fibre optical cables.

4. Router: routes data to its destination using IP address

5. Hub: Used to broadcast data to all its ports and then sends it to the destination computer on a network. Incase the hub fails to perform this duty the entire network will be at a halt.

6. Switches: Look like hubs but are more advanced. they are used to process switching tables inside of them which store the MAC address of every computer coonected to it. it later sends data only to the requested address unless the hub broadcasts data to all its ports.

7. Gateway. Its a device used to connect local area network(LAN)to internet. Used to provide security to the network by monitoring the incoming and outgoing traffic to avoid any malicious activity within the network.

System unit

This is a case that houses most of the electronic components of a computer. Some of the hardware housed in the system unit include:

1. Motherboard or system board: Its the main circuit board in the system unit that contains most of the electronic components of a computer.

2.Central processing unit(CPU): this is the brain of a computer which performs processing tasks and controls all other activities of a computer.

3.Memory:It refers to integrated circuits that temporarily store program instructions and data eg RAM. Other memory locations include ROM, BIOS, CMOS(complementary metal oxide semi-conductor) battery used to retain information when poer is off,stores the computers start up information and time plus the data on the computer.

Memory has different slots e.g SIMM and DIMM.

4. Expansion slots: These are sockets on the motherboard into which adapters are connected for example;

(a)video card Allows a computer to display video, graphics and animations. A video card with video digital camera allows the user to watch a live video however to watch videos on line requires high speed internet connection.

(b) sound card produce sound like music and voice.

(c) network interface card(NIC)or Network adapter: It acts as an interface between a computer and network cable and used to prepare, send and control data on the network. It has indicator lights(LED)for example the green LED indicates shows the card is recieving electricity. The orange and red LED indicates network connectivity. It allows computers to communicate.

(d) modem card(Modulator- Demodulator)used to translate data from digital to analog and vice versa. This is because if data is to travel over a telephone line, it must be analog in nature and a computer uses digital data.

5. Buses or IDE cable: used to connect hard disk, cd-ROM and other drives on the motherboard. They are electrical path way through which bits are transmitted between computer components in a computer system. the size of a data bus determines the amount of data that can travel through the pipe line at one time.

6. Power supply:supplies power to the motherboard and other internal devices. It converts the wall outlet electricity to lower voltages used by the computer. To connect computer to main power outlet cables are used for example parallel cables,serial and USB cables, interface cable used to connect peripheral devices to the motherboard ie one end connects to device and the other to the motherboard.

7. Ports and connectors: A port is a socket used to connect peripheral or external devices to the system unit for example

1.keyboard port 2.USB(univeral serial bus) Is a serial cable replacing old serial and parallel cables because it supports a wide range of peripheral devices. 3.serial port 4.monitor port port port 7.mouse port 8. parallel port 9. speaker port 10.microphone port

Connectors are found at the end of a cable and used to attach it to peripheral devices. There two types of connectors; i.e male connector with exposed pins and Female connectors have small holes to accept the pins.

Ports are also in different types e.g;

(a) Serial ports: Used to transmit one bit of data at a time and connect low speed connect monitor , modem, keyboard.

(b) Parallel ports: Connect devices that transmit large amounts of data for example a printer, disk or tape drives etc. parallel cables transmit information simultaneously using a set of many wires.

8. Coprocessor: Its a special circuit board designed to perform a specific task eg calculations etc. Its mainly used to increase the speed at which tasks are processed.

9. Disk drives:eg hard disk, floppy drive CD/DVD drive.

10. Fun Used to cool components inside the system unit.

11. Heat sink used to remove heat from during processing operation to ensure safe operating temperatures. Over heating of a component reduces its life span and can result to system freezes.

The central processing unit(CPU)

The CPU is the brain of the computer which performs processing tasks and controls all acitities of the computer.its housed inside the system unit and mounted on the motherboard. The configulation or setup of the CPU dertermines whether the computer is very fast or slow.

The central processing unit is composed of three different functional units namely; 1. Arithmetic and logic unit. 2. control unit 3. Main memory or processing registers. all the above units are controlled an electronic component called a bus which acts as an electronic highway between them.

Arithmetic and logic unit (ALU)

It is where all arithmetic and logic operations are carried out. Arithmetic operations include addition, subtraction, division and multiplication. The logic functions or operations include >, <, =, >=, etc used to make comparisons between values in order to determine which instruction should be executed. ALU has temporary storage locations called registers that store data before and after processing.

Control unit

It directs and coordinates all processing activities in the CPU as well as input, storage and output operations. the control unit involves a machine cycle for fetching , decoding , executing and storage of data.

Diagram illustrating the machine cycle

Fetching is used to obtaining the next program instruction from memory. Decoding is translating the program instruction into commands that the computer can process.

execute is the actual processing of computer commands.

Store its where the result of instruction is written to memory.

Note: fetching and decoding is part of the cycle called instruction cycle while execution cycle is composed of executing and storing.

To control activities, the control unit uses a system clock to control the timing of all computer operations. A system clock is a chip that generates electronic pulses at a fixed rate. therefore the faster the clock pulses, the faster the CPU and computer in processing data.

Main memory or processing registers

Memory refers to integrated circuits that temporarily store program instructions and data to be retrieved. Main memory or primary storage is a storage location for data and instructions accessed by the control unit.

Memory stores three types of items;

(i) The system software that directs and coordinates the computer equipment.

(ii) The application program instructions that direct the work to be done.

(iii) Data being processed.

Memory size measurements; Memory can be measured in the following ways

1. Bit its the basic unit of memory

1. Byte = 8 bits.

2. Kilobyte(KB)= 1024bytes or 1000 bytes.

3. Megabyte(MB) = 1 million bytes

4. Gigabyte(GB) = 1 billion bytes or 1 million kilobytes

5. Terabyte = 1 trillion bytes


There two categories of memory;

1. ROM (Read Only Memory)

2. RAM( Random Access Memory)


It is used to store program instructions and data permanently or semi permanently. The instructions stored here do not change e.g the booting instructions or instructions that start a computer.

Characteristics of ROM

1. Its content can be read but cannot altered unless it is a special type of ROM. The instructions stored in ROM memory are called firmware.

2. Non-volatile ie its content is not lost when the computer is switched off.

3. Stores permanent or semipermanent instructions from the manufacturer. The semi permanent instructions are those ROM chips that can be programmed according to the user's specifications.

Types of ROM

(i) MROM(mask read only memory): Its content cannot be changed once its written on by the manufacturer.

(ii) PROM( programmable read only memory). It can be altered by the user only once after the content is written on it. once programmed and the instructions are stored, it can never be altered.

(iii) EPROM(Erasable programmable read only memory): Its content can be erased by exposing it to ultra violet light and reprogrammed for another use. After reprogramming they cannot be altered.

(iv) EEPROM(electronic erasable programmable ROM)

This type can be erased and reprogrammed using electricity. A user can put instructions in memory as many times as he can and these instructions can be altered. The devices using EEPROM include mobile phones with memory for storage of phone and names which can be altered or erased, others are color TV's etc

EEPROM chips retain information ADVANTAGES OF ROM

1.Convinient for example the more instructions in ROM, the fewer floopy disks one will handle.


1. It is expensive to manufature ROM chips and recording data on them. Therefore manufacturers record only those instructions that are crutial to the operation of the computer.

2. Information cannot be changed was it has been programmed. Incase one needed to upgrade it, then it had to be removed from the computer which was an inconvinience.

RAM(Random Acess Memory)

It is the common type of main memory characterised by the following factors;

1. It is a temporary or volatile storage ie tis content is lost when the computer is switched off.

2. Data can be read and written in it.

3. The user can ditacte what is to be contained in RAM.


There are two types of RAM namely;

(a) Static RAM

It is used to hold content as long as there is power, it is faster compared to DRAM, more expensive and mostly used to make special memory types.

(b) Dynamic RAM

Used to hold content for a short time even if power is on. It can be maintained by designing a memory chip in a way that its content is automatically rewritten several times per second.


special purpose memories are found inside the CPU or input and output devices. They help to increase the overall performance of data and instructions moving in and out of the CPU. Such memories include;

(i) Buffers: These are areas of memory used to store data temporarily that has been read from an input device and data waiting to be sent to an output device. Buffers set the CPU free to perform other activities by temporarily holding that data.

(ii) Registers: These are storage locations in the CPU that temporarily store specific data or one piece of data at a time. Registers accept, store and transfer data and instructions that are being used immediately. The size and number of registers in the CPU vary according to CPU design which affects the processing power of a computer. for example the larger the register, the more bits it can handle hence greater processing power.

Examples of registers include;

(a) An accumulator which temporarily holds the results of the last processing step of ALU.

(b) Instruction register: temporarily holds an instruction just before it is interpreted into a form that the CPU can understand.

(c) Address register: holds next piece of data waiting to be processed.

(d) Storage register: holds a piece of data that is on its way to and from the central procesing unit.

(iii) Cache memory It is a high speed access memory where data accessed frequently by the processor is stored. its used to provide space for temporary storage of frequently accessed data. Cache is more expensive than ROM and RAM but makes the computer more powerful. It has limited storage capacity therefore old data is replaced when new data as it is recieved.


1. It stores a copy of the main software (operating system)that controls the operations of the computer.

2. Temporary storage of application program instructions to be retrieved by the CPU for interpretation and execution.

3. Stores data that has been input from the keyboard or other input devices until its transfered to the CPU for processing.

4. Stores information produced after processing from the CPU until its transfered to output devices e.g monitor, printer or storage devices.

CMOS( complementary metal oxide semi-conductor) memory:

It is used to store information about the computer system that is needed each time the computer is started. for example information about amount of memory, type of hardware devices of the computer, type and capacity of disk drives. keeps track of date and time on computer by operating the real time clock.

Characteristics of CMOS

- stores information when the computer is turned off.

- data can be changed when new device is added to the computer system.

- very low electrical requirements and can be powered by a battery.

Qn. What determines the processing power of the computer?

1. register size.

2. clock speed this controls the timing of all computer operations. it determines the speed at which a processor executes instructions. The clockspeed is measured in hertz.

3. data bus capacity. A bus is an electrical pipeline through which bits are transmitted between computer components in the computer system. The size of a data bus determines the amount of data that can travel through the pipeline at one time. hence affecting the computer's performance.

NOTE: BIOS(basic input output system) i also a special proggram that directs the power on self test(POST)


Software refers to instructions that directs a computer to perform the tasks necessary to process data into information. It can also be defined as a set of computer programs that guide the computer in its operations. computer software is categorized or classified according to purpose ie the tasks its used to perform and according to acquisition ie the way software is obtained.

There two main categories of software:

  • system software
  • application software

System software

Refers to all programs including the operating system that are related to control the operations of computer hardware. The functions of system software include:-

1. Booting or starting a computer to ensure that all hardware is working properly.

2. Loading, executing and storing application programs.

3. storing and retrieving files

4. performs system utility functions eg formatting disks, sorting data files etc.

5. translating program instructions into binary language

System software is divided into different categories which include operating system, utility software, networking software and programming languages or languages translators.

Operating system(OS)

It is the main program on the computer.It refers to a set of programs that manage the operations of a computer and acts as an interface or go between the user , application programs and computer hardware. It also manages the input, output and storage operations in the computer, controls flow of data to and from the peripheral devices etc.

The OS is stored on the hard disk and each time a computer is started the essential and more frequently used instructions are copied to computer's memory from hard disk. These essential instructions are called master program or kernel or resident portion. On the other hand less frequently used instructions are called external commands.

Examples of operating system include microsoft windows 95/98/2000/2003/2007, windows NT, ME (windows millenium edition), XP (windows eXperience),windows vista,windows 3.X, linux which is also in different versions like caldera, debian, mandrake, red hat etc, unix, macintosh, OS2, Microsoft DOS(disk operating system),windows CE( windows embedded compact) etc

Functions of the operating system

1. Memory management

The operating system organises main memory into partitions for storing items like the kernel, application proggrams and data waiting to be processed. It allocates items to areas of memory called buffers and can locate each data item. It also monitors content of items in memory and deletes those items nolonger needed by the CPU.

It also uses the swap file to store items during processing.

NOTE: A buffer is an area in memory in data waiting to be transfered to and from an input or output device is placed.

2. Spooling print jobs

The print jobs are sent to buffer before being printed. the print spooler program manages and interpretes print jobs and places them in a queue. therefore multiple print jobs can be lined up in a buffer.

3. monitoring system performance

The operating system monitors the status of computer system and performs error checks on both hardware and software. the performance monitoring software is used to access and report information about various devices of computer system. such information is useful in identifying problems of devices.

4. Job scheduling

The OS determines which task should be processed first before the other and monitors it. The processor will process one task at a time and smaller tasks will be processed before the larger ones.

5. Resource control and allocation

The operating system ensures that it avoids deadlocks ie a situation where a particular task holds a needed resource and refuses to release it for use by other tasks. Therefore resource control and allocation is the function of an operating system because it determines which task uses a particular resource and at what time.

The operating system arranges resources according to priority and gives each resource an interrupt number which is unique. Therefore a resource with higher priority is granted more control over a resource in case another resource requets for the same.

6. Input and output management

The OS manages the input , output and storage processes in the computer by ensuring that data is flowing properly up to its destination. this can be an output or storage device etc.

7. Administering security

There operating systems that allow users to provide password in order access resources on computer system. they also keep a record of the sucessful and unsucessful logon.

8. Configuring the computer devices.

There many operating systems that allow one to configure devices automatically because they support plug and play.It will then proceed by loading the drivers of that particular device and check if they do not conflict with already installed drivers.

NOTE: Drivers are small programs which tell the operating system how to communicate with a device.

Plug and play(PnP)Is where the computer recognizes a new device plugged into it and assists in installing its drivers automatically and cheking conflict with existing drivers.

9. manages the storage devices for example copying data on a device, retrieving information, sorting files and renaming them, deleting files , checking disk space on the hard disk, formatting disks etc

10 The operating system determines the best IRQ(interrupt request number)to use when communicating to the Central processing unit. This happens when processing of instructions in a particular program is interrupted because of an external request. when the OS requests a cuurent task to be processed because its IRQ, the processor will stop executing the instructions it had been processing and can resume later after processing the current instruction(s). The above process is called interrupt handling.

Resources controlled by the operating system

1. processor

2. RAM( main memory)

3. input and output devices and ports

4. secondary storage devices

5. communication devices


Operating systems are classified into different categories;-

1. Number of tasks it can handle at the same time. These include; (i) single program operating system This allows processing of only one user program in RAM therefore to run another program the user must exit from the already running program. eg MS DOS

(ii) Multi tasking operating system

A multitasking operating system allows a single user to work on two or more applications that reside in memory at the same time for example windows 2000, unix and linux. the central processing unit gives a time slice for the different applications running by swicting its attension to the different programs as it recieves requests to process and execute.

2. Number of users.

(i) Single user operating system A single user operating system allows only one user to run one program at a time.

(ii) Multi user operating system

A multiuser operating system enables two or more users to run a program simultaneously on a given computer. examples linux, unix and windows 2000 etc

(iii) Multiprocessing operating system can support two or more CPUs running programs at the same time.

3. HCI (Human Computer Interface). This refers to the way of interation between the user and the computer and how easily they can operate it. some interfaces are usefriendly while others are difficult to manipulate especially those which require the use of commands.

(i) command line interface (CLI) It is a mechanism for interacting with a computer's operating system or software by typing commands to perform specific tasks this can be done with the use of a keyboard. Therefore the set of commands a user uses to interact with the computer is called the command language. Examples of software with command line interface include Microsoft DOS(disk operating system), Unix shells

Advantages of a command-line interface include

1. It takes little memory and normally does not require a very fast processor.

2. Operation is fast because commands can be entered directly through the keyboard.

3. Many commands can be grouped together as a batch file so that repetitive tasks can be automated.

Disadvantages of a command-line interface include

1.The user have to learn and memorize the commands.

(ii) Menu driven interface this has a list of options to choose from . It is therefore good for users because it does not require use of commands. however it should be noted that some menu interfaces are complicated like in in DOS shell.

(iii) Graphical user interface(GUI)

This is a type interface which allows people to interact with programs in many ways. They use menus and visual indicators like icons, buttons plus other objects in order to issue commands. They are therefore user friendly. Examples of operating systems with GUI include windows 98, windows CE etc

Advantages of a graphical user interface include

1. A graphical user interface is user-friendly because it is easy to

learn and work with.

2.There is no need to type and memorize any command language.

The interface is similar for any application.

Disadvantages of a graphical user interface include

2. A graphical user interface normally requires more memory as well as a faster processor.

3. It also occupies more disk space to hold all the files for different functions.

4. It is difficult to automate functions for expert users.


1. Hardware configurations this includes the memory capacity a computer, processor type, capacity of the hard disk etc

2. Applications intended to be installed on the computer.

3. Human computer interface.

4. The cost of the operating system and its availability in the market.

5. Reliability ie one which runs with out stopping to respond.

Utility software

It is a type of system software that performs a specific task, usually related to managing a computer, its devices or and its programs.

The utility software is in different types for example the system utility software which help a user work with the operating system and its functions. the application utility software helps in the efficient use of the application software.

Examples of utility software include

(i) Disk defragmenter

A disk defragmenter is a utility that reorganizes the files and unused space on a computer's hard disk so that data can be accessed more quickly and programs can run faster therefore increasing efficiency. it detects computer files whose content has been stored on the hard disk in fragments and reorganizes it. When the contents of a file are scattered in different noncontiguous sectors we say the file is fragmented.therefore the process of defragmenting is reorganizing the disk so the files are stored in contiguous sectors.

(ii)Disk cleaner and scan disk are examples of disk scanner utility software. they are used to scan the contents of a hard disk to find files or areas that are corrupted or not correctly saved, and eliminate them for a more efficiently operating hard drive. for example a scratch can be the reason why data disk cannot be stored in that location and also it could be a corrupted FAT files (file allocation tables)

(iii) disk compression software can transparently compress or uncompress the contents of a disk in order to increase its capacity. It is some times called file compression software.

(iv) Backup software makes a copy of all information stored on a disk, and restore either the entire disk in case of disk failure or selected files in an event of accidental deletion.

(v)Disk checker

(vi) An anti virus utility is a program that prevents, detects, and removes viruses from a computer's memory or storage devices for example Norton AntiVirus. A virus in a computer system can modify the programs instructions. however the antivirus utility records its file size and file creation date in a separate inoculation file and uses the information to detect in case a virus alters the program file. An infected file which cannot be removed is placed in a separate area of a hard disk until it will be removed.

antivirus utilities can create a recovery disk to remove or repair infected programs and files in some cases it will require that the hard disk be reformatted

(vii) Screen savers it a utility software that causes the monitor's screen to display a moving image or blank screen if no keyboard or mouse activity is taking place for a specified time period.

(viii) Disk partitioner Used to divide an individual drive into multiple logical drives each with its own file system which can be mounted by the operating system and treated as an individual drive.

(ix) File conversion software is used to convert a file from one format to another so that it can be used by another application.

(x) file viewer utility software helps to display files and also copying content of a file.

(xi) A diagnostic utility This is used to compile technical information about a computer's hardware and some system software programs after which it makes a report outlining any identified problems. for example Dr. Watson as a diagnostic utility in Microsoft Windows XP

Programming languages

A programming language is the way of communicating with the processor. There are two basic categories of programming languages;

1. low level languages

Low level languages includes two types the machine language and assembly language. These languages do not need a compiler or interpreter in order to run. Machine language is a first generation language with the machine code and its directly understood by the microprocessor. characterized by the following factors:-

  • its difficult to learn and be understood by humans.It requires one to memorize the numerical codes for every instruction used.
  • Not user friendly
  • Programming in machine language is tiresome.
  • Many errors can be created.
  • Instructions in machine language are represented in binary format.

Assembly language:

It is a second generation language which is an improvement over the machine language.

Programming in this language must be translated to machine code a computer understands using an assembler program. the original assembly code is called the source code while the final output of a machine code is the object code.

  • Easy to understand and be remembered by humans.
  • the disadvantage of assembly language is that it depends on the registers and memory locations on the computer. Hence the language cannot be transfered from one computer to another due to difference in processors.

Advantages of low level language.

  • the processing speed is high as there is no need to translate the instructions.
  • it occupies less memory space.
  • No need to translate the program because the instructions are already in machine code for the machine language.


  • Difficult to read , write and understand.
  • They vary from machine to another.
  • Requires people who understand the language to operate.
  • difficult to code
  • One has to remember the address sequence of different instructions.
  • Not easy to debug.

2. High level languages These are machine independent and require a translator. They are third generation languages used for specific functions or operations it could be business etc. examples include Pascal, COBOL(Common Business Oriented Languages), C, C++, BASIC( Beginners All Purpose Symbolic Instruction Code) etc. Since these languages are designed to solve particular problems they are referred to as problem- oriented languages. The language processors are used to translate high level languages to low level languages which can be understood by the machine or processor. these include compilers, assemblers, interpreters and linkers.

Assemblers These programs recognize the string of characters that make up symbolic names of various machine operations and substitutes them with the machine code. this is done until all instructions have been translated.

Compiler translate the program into machine language at once during the compilation time while as the interpreter translates line by line when the program is running. This is done every time the program is executed. therefore interpreters are slower than compilers in translating of program instructions. On the other hand the compiled code runs more slowly and uses more memory compared to assembly languages.

Linkers are user to combine the compiled programs and find a location where they can be stored in memory. this is done by creating files for such instructions.


  • They are easy to read , write and understand for example the instructions are written in English language.
  • its easy to debug
  • One has to remember the addresses of different instructions.
  • The language is common for all machines because its language independent.

However high level languages have a low processing speed and occupy more memory space.

Key words

syntax: refer directly to the rules and principles that govern the sentence structure of any individual programming language.

Semantic: It involves the study of meaning of a word or phrase, usually in language.

Debugging: Is tracing and eliminating all the errors in a program.

Source program: these are the original words a programmer writes during programming.

Object code: are programs generated from the source program.

Pseudo-code: Are programming statements with a mixture of human language and computer language which is used to represent programs.

Networking software

This is the software which helps computers to communicate which enable exchange of data and hardware. The network software can be embedded with in an operating system while others are independent. examples include novel,


A firmware is a chip that is used to hold the operating system, utility programs and language translators. these chips are mounted on the motherboard of the computer.

Application or programme software

These application packages that are designed to help the user accomplish specific tasks. They are into different groups for example the in-house developed software and standard software.

In-house developed programs

They are programs that are designed by hired programmers to meet particular user's need e.g company or organization.

Standard software

These are software programs that are designed, packaged and made available for purchase through vendors or distributors. This software can be integrated (suite) or single purpose software.

Advantages of system software over the in-house developed software

1. Standard software can easily be installed and run on a computer.

2. They are already available for any task the user may need.

3. They rarely have errors because of being tested first before releasing them on market.

4. The software programs can be modified to meet the diiferent users needs.

5.They are not expensive as the in-house developed software.

Examples of common application packages used include

1. word processor

This is a software used to create documents e.g letters using mail merge, mail labels,they are also used to create graphics and web pages etc. Examples of word processor include microsoft word, word perfect, wordpro, word star

2. Spreadsheet

It is a software mainly used for calculations using the predefined formulars. The most popular ones are micosoft excel, lotus 1,2 and 3, corel Quattro pro etc

3. Database software

Is one which allows users to create an organized collection of data for easy access, retrieval, management and use. They are mainly used to store records. Examples include microsoft visual foxpro, microsoft access, Borland DBase, corel paradox etc

4. Presentation

Presentation software is used to create presentations to be used in communicating information to a big audience. examples include microsoft powerpoint, corel presentation etc

5. Desktop publishing

It is a software used to produce high quality text and graphics with attractive colors for example news letters etc. Examples include microsoft publisher, adobe pagemaker, adobe indesign etc

6. Project management

This is a software used in project planning to schedule the various tasks and the resources plus costs that will be needed to accomplish the various tasks. Microsoft project is an example of such software.

7. Accounting software

Used by companies to record and report their financial transactions for example prepare account payable and recievable, making payrolls etc. Examples include Intuit QuickBooks etc

8. Entertainment software they include interactive games, videos, and other programs designed to support a hobby etc

9. Educational software

These are designed to teach particular skills or displines to the learners. some can have quiz to test the laerners understanding of the concepts.

10. Video and Audio editing software

Used to create and modify video plus audio clips. One can reorder a series of their clips and add special effects to them. Popular video and audio editing software include Adobe Premier, Ulead VideoStudio etc. Entertainment software

11. communication software

Are programs that help to establish a connection to another computer or network and manage the transmission of data, instructions, and information between computers and other devices. For example email software, video conferencing software, chat software, web browser etc.

12. Utility programs.

These are programs used to manage the computer hardware and software of the computer eg antivirus utility software, screen saver etc

13. Computer aided design can be used for technical drawing, engineering and architectual designs

14. Computer aided design like autocad are mainly used for technical drawing.



1. authenticity:

The software to be bought should be a genuine, valid and legal copy with a developer's licence this is to avoid pirated copies.

2. the user needs: the software to be bought should in accordance to what they user is to use it for. It could be any application program and an operating system.

Word processor

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students should be able to understand the following

  1. Define the term computer hardware
  2. Identify the different hardware components of a computer
  3. Identify the peripheral devices of a computer
  4. Classify the hardware components
  5. Students to know the uses of different hardware devices

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There some sample questions on computer storage mediums

1. The process of saving information onto secondary storage devices is referred to as a. backing up c. writing b. restoring d. reading 2. The amount of time required by a storage device to retrieve data and programs is a. access c. memory b. capacity d. storage 5. Thick, rigid metal platters that are capable of storing and retrieving information at a high rate of speed are known as a. hard disks c. cartridge b. soft disks d. pack 6. An internal hard disk is also known as a ____. a. platter disk c. rotating disk b. fixed disk d. read-write disk 7. A(n) ____ is a hard disk that can be removed from the system unit. a. internal hard disk c. hard disk pack b. hard-disk cartridge d. megabyte drive 8. A group of external disk units connected to a microcomputer to provide additional storage are called a. access limited disks c. access disk packs b. hard disk packs d. grouped storage disks 9. The term for the process of storing frequently used data from a disk into memory is a. data compression c. disk caching b. data access d. RAID 10. A CD-R stands for a. CD-rewriteable c. CD-reader b. CD-recordable d. CD-read only 11. A CD-ROM disk a. cannot be erased and rewritten c. holds less data than a floppy disk b. has more storage capacity than a CD-R d. can be written to only once

13. A DVD device can store a. as much data as a CD-ROM b. as much data as 100 3 ½” floppy disks c. over two hours of high quality sound and video d. digital data, such as sound and video, in an expanded format 14. DVD stands for ____ a. digital video data c. digital versatile disk b. direct video disk d. direct versatile disk 16. This type of storage device has no moving parts. a. hard disks c. optical disks b. floppy disks d. solid state

21. RAM is sometimes referred to as sequential storage. 22. Floppy disks are considered high capacity disks. 23. A file that is 1600 KB will fit on a traditional floppy disk. 24. The traditional floppy disk is 1.44 GB. 25. A head crash is caused when the user enters an incorrect disk request. 26. For most microcomputer systems, the internal hard disk drive is designated as the D drive.

Part C: Completion Complete each sentence or statement. 31. ____________________ is the process of accessing information that is stored on a storage medium. 32. ____________________ speed is the measure of the amount of time required by a storage device to retrieve data and programs. 33. Flat, circular pieces of Mylar, used as removable data storage media, are called ____________________. 34. ____________________ disks are produced by Iomega and are a type of removable medium with 100 MB, 250 MB or 750MB of storage.

36. Increasing storage capacity by reducing the amount of space required to store data is called file ____________________.

38. Access to data on media-like cassette tapes, where records are stored one after another, is ____________________ access. 39. Media that allow records to be retrieved in random order provide ____________________ access to data.

41. Explain the difference between volatile and nonvolatile storage, giving an example of each. 43. Explain sectors and tracks. 44. List two advantages internal hard disks have over floppy disks. 45. Describe how disk caching improves hard disk performance. 47. Explain how file compression is performed. 48. Describe DVD technology. 49. What are flash memory cards used for? 50. Contrast sequential access with direct access.

  1. what is the meaning of the phrase "computer hardware"

Is every one conviced with that definition? if not please give us your opinion