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information technology > Fundamentals of Hardware and Software > Flashcards

Fundamentals of Hardware and Software Flashcards

1
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A
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2
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3
Q

the major hardware components of a computer
system

A

Central processing unit
Control Unit
Arithmetic and Logic Unit (ALU)
Main Memory
secondary storage
Peripheral Devices
Input Devices
Output Devices

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4
Q

function of the Central processing unit

A

Central processing unit: The CPU is also called the processor. It takes raw data, follows a set of instructions (programs) and converts it into information. The CPU consists of two smaller units known as the control unit (CU) and the arithmetic and logic unit (ALU).

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5
Q

function of Control Unit

A

Control Unit: This is the main part of the CPU. It directs and coordinates all activities within the CPU. It determines the sequence in which instructions are executed.

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6
Q

function of the Arithmetic and Logic Unit

A

Arithmetic and Logic Unit (ALU): The ALU performs all the arithmetic and logic functions in a computer. The arithmetic operations include addition (+), subtraction (-), multiplication (*) and division (/).

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7
Q

function of input

A

Input Devices: Input devices are any device that is used to put data and instructions into the computer.

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8
Q

function of the main memory

A

Main Memory- Main memory is also called computer memory, immediate access storage (IMAS/IAS) or primary storage. This unit of memory is directly accessible to the CPU. It holds data and instructions that the computer is processing at the time.

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9
Q

function of the secondary storage

A

secondary storage: Secondary storage is also called auxiliary storage, backing storage or disk storage. These devices are used to store data and instructions when they are not being processed. Secondary storage is more permanent than main memory, since data and instructions are not lost when the power is turned off. It is also much cheaper than primary storage and is unlimited since you can have as much of it as you can afford.

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10
Q

function of the output devices

A

Output Devices: Output devices are any device that is used to get information out of a computer.

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11
Q

Function of peripheral devices

A

Peripheral Devices: Peripheral devices are any device controlled or monitored by the CPU. It includes both input and output devices.

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12
Q

The CU executes an instruction by performing the following steps:

A
  1. Fetching the instructions from memory
  2. Decoding the instructions
  3. Fetching the data required by the instructions from memory
  4. Sending the data and instructions to the ALU for processing
  5. Sending the data to memory after processing
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13
Q

The logic functions are comparisons, such as

A
  1. Equal to (=)
  2. Not equal to (≠)
  3. Less than (<)
  4. Greater than (>)
  5. Less than or equal to (<=)
  6. Greater than or equal to (>=)
  7. AND
  8. OR
  9. NOT
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14
Q

what is a memory chip

A

A memory chip is an integrated circuit (IC) made up of millions of transistors and capacitors.

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15
Q

Primary storage consists of two types of memory chips:

A

RAM
This chip is used to hold data and instructions (programs) temporarily while processing is taking place using that data and program. It also holds the data that results from processing – data that is waiting to be output or stored in a secondary storage device. RAM is volatile i.e.; it is temporary and changeable. If the power is turned off or the computer is rebooted (started up again) all the information held in RAM will be lost.

ROM
This chip holds data and instructions necessary for starting up the computer when it is switched on. It is used to store system-level programs such as the BIOS (Basic Input Output System) program.

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16
Q

variations of ROM

A

Programmable ROM (PROM)
This type of ROM can be programmed only once using special equipment. It is useful for companies that want to make their own ROMs from software they write themselves. If they change their code, they can create new PROMs without requiring a ROM manufacturer.

Erasable programmable ROM (EPROM)
This type of ROM can be erased and reprogrammed, which makes it more useful than a PROM. EPROM chips are programmed in the same way as PROM chips. Data is erased from this chip by exposing it to ultraviolet light of a specific frequency for a specified period of time.

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17
Q

Secondary storage devices are chosen for a particular use based on their:

A
  • Storage capacity (how much data the device can store)
  • Access speed (the time needed to locate the data and transmit it to the CPU)
  • Portability (ability to be easily removed and used on another system)
  • Cost
  • Size (necessary for storage on shelves or portability)
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18
Q

Magnetic tape

A

A magnetic tape looks like an audiocassette tape. Tapes may come in different sizes. It is used mainly to backup hard disks because it can store large amounts of data at a low cost. Accessing data on a tape is very slow since data is stored sequentially. Sequentially means that data is retrieved in the order which it was stored. As of 2008, the highest capacity tape cartridges can store 1 TB of data. A tape drive is used to read data from and write data to the tape. The tape drive may be external or built into the system unit.

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19
Q

All magnetic disks provide direct access to stored data. what is direct access

A

This means that you can go directly to specific piece of data without having to access any other either before or after the data you want.

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20
Q

floppy disk

A

This is also called a diskette. It is a removable, flexible plastic disk, coated with a magnetisable material. The disk is held in a plastic case, usually 3.5 inches by 3.5 inches in dimension. The plastic case protects the disk from dust and grease. The floppy disk is used to store and transfer small amounts of data between computers. A 3.5-inch floppy disk holds up to 1.44 MB of data.

Data and information are written to or read from the disk by a read/write head in the disk drive held in the system unit. Data is stored on both sides of a diskette on tracks and sectors.

Before data is stored on a floppy disk, it needs to be formatted.

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21
Q

tracks & sectors

A

Tracks are a set of numbered concentric rings. The tracks are also divided into wedge shaped pieces known as sectors, which are also numbered. A sector is the amount of data that can be read from or written to a disk by the computer in one read/write operation.

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22
Q

Formatting

A

Formatting means writing electronic information on the disk so that the computer can recognize the disk as a valid storage device where data can be stored.

Most floppy disks are already formatted when they are purchased. If a diskette is formatted after data has been stored to it, the information will be deleted.

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23
Q

hard disk

A

A hard disk is a thin but rigid, inflexible disk made of highly polished metal. The surface of each side of the disk (also called platters) is covered with a substance that can be magnetized. As of April 2009, the highest capacity HDDs is 2 TB.

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24
Q

types of disks

A

There are different types of disks:
moveable head, fixed head and external.

Moveable head hard disks have one read/write head per disk.

Fixed head disks have a read/write head for every track on the disk.

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25
Q

optional disks

A

Optical disks are disks that are read by laser lights. They are made from plastic. The data is stored on layers inside the plastic.

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26
Q

two main types of optional disks

A

CDs and DVDs are the two main types of optical disks

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27
Q

compact disk

A

A Compact Disc (CD) is an optical disc used to store digital data. The physical dimension of a CD is 12 cm or occasionally 8 cm in diameter. CDs can hold up to 750 MB.

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28
Q

3 types of compatic disks

A

They are three types of CDs: CD-ROM, CD-R and CD-RW.

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29
Q

CD-ROM (read only) uses

A

This type of CD is used for:
* Storing multimedia (text, graphics, sound and videos).
* Storing software packages for sale or distribution e.g., application software packages such as encyclopedias, word processors, training programs, games and graphics packages.

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30
Q

CD-R (recordable) uses

A

CD-R (recordable)

This type of CD is used for:
* Storing large volumes of data that does not need to change e.g., music CDs.

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31
Q

CD-RW (re-writeable) uses

A

CD-RW (re-writeable)

This type of CD is used for:
* Storing large volumes of data that change frequently e.g., backups copies

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32
Q

DVDs

A

“Digital Versatile Disc” commonly called “DVD” is an optical disc storage media that can be used for storing movies with high video and sound quality. DVDs look like compact discs; their physical dimensions are the same (12 cm or occasionally 8 cm in diameter). DVDs are encoded in a different format to CDs and they have a much higher density (more data is stored per unit area). Some DVDs are double sided i.e., they can hold data on both sides. DVDs can hold between 4.7 GB and 17 GB of data.

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33
Q

3 types of DVDs

A

Three types of DVDs are the DVD-ROM (read only), DVD-R (recordable) and DVD-RW (rewritable).

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34
Q

floppy disks

A

USB Flash drive
USB Flash drives are storage devices which consist of a small circuit board encased in a plastic or metal casing built with a USB interface. They are typically small, lightweight, removable and rewritable. As of November 2006, to present, memory capacities for USB Flash drives range from 32 MB up to 64 GB. Flash drives are more compact, generally faster, hold more data and may be more reliable (due to their lack of moving parts) than floppy disks.

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35
Q

floppy disk uses

A

Common uses
1. Personal data transport
The most common use of flash drives is by individuals to transport and store personal files such as documents, pictures and video.

  1. Computer repair
    Flash drives are used to transfer recovery and antivirus software to infected PCs.
  2. System administration
    Flash drives are used by system and network administrators, who load them with configuration information and software used for system maintenance, troubleshooting, and recovery.
  3. Application carriers
    Flash drives are used to carry applications that run on the server computer without requiring installation.
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36
Q

flash memory cards

A

These come in the form of a card shaped like a stick of chewing gum, with dimensions 21.5 x 50 x 2.8 mm and storage capacities up to 64 GB. They are a special type of EEPROM that can be erased and reprogrammed in blocks instead of one byte at a time. They are used in PDAs (personal digital assistants), laptop computers, digital audio players, digital cameras, mobile phones and video game consoles.

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37
Q

Storage Device, Storage capacity, Advantages & Disadvantages
magnetic tape

A

Capacity
Up to 1 TB

Advantages
* Easy to transport and store
* Cheap
* Mostly used for backup or archives

Disadvantages
* Provides sequential access to data stored
* Limited shelf-life (2 years)
* Must be stored in a suitable environment (smoke, dust, temperature and humidity must be carefully controlled)
* Difficult to update files (cannot make changes to a record without writing over the entire tape)

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38
Q

Storage Device, Storage capacity, Advantages & Disadvantages
floppy disk

A

Capacity
1.44 MB

Advantages
* Provides direct access to data stored
* Small and very portable
* Easy to store
* Suitable for backing up small files
* Data security (e.g., you can store small files that you don’t want other computer users to see)

Disadvantages
* Small storage capacity (unsuitable for storing files containing graphics)
* Limited shelf-life (2 years)
* Slow to read/write speeds

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39
Q

Storage Device, Storage capacity, Advantages & Disadvantages
fixed hard disks

A

Capacity
Up to 2 TB

Advantages
* Direct access
* Fast data transfer speeds
* Vast storage capacity

Disadvantages
* Not portable

40
Q

Storage Device, Storage capacity, Advantages & Disadvantages
Removable hard disks

A

Capacity
Up to 1.5 TB

Advantages
* Direct access
* Fast data transfer speeds
* Vast storage capacity compared to diskettes
* portable

Disadvantages
* computer must have a USB port

41
Q

Storage Device, Storage capacity, Advantages & Disadvantages
Optical disks

A

Capacity
CD: up to 8MB
DVD: up to 17 GB

Advantages
* Direct access
* Fast data transfer speeds
* Vast storage capacity compared to diskettes
* Portable
* Can be cleaned easily with a soft cloth
* Unaffected by magnetic fields

Disadvantages
* Data on CD-ROMs cannot be changed
* Access times are slower than hard drives

42
Q

Storage Device, Storage capacity, Advantages & Disadvantages
Flash memory

A

Capacity
Up to 64 GB

Advantages
* Physically very small
* Highly portable
* High data transfer speed to PCs
* Large storage capacity compared to diskettes
* Direct access

Disadvantages
* May need special software to be used with PCs
* Limited storage compared to CD or DVD

43
Q

Device Interfaces
These are connectors and cables used to transfer data from the CPU to input, output and storage devices. There are different standards or technologies used to design these devices. Three main standards used are:

A

Small Computer System Interface (SCSI)
It is a set of standards for physically connecting and transferring data between computers and peripheral devices. SCSI is most commonly used for hard disks and tape drives, but can connect a wide range of other devices, including scanners and CD drives.

Intelligent Drive Electronics or Integrated Drive Electronics (IDE)
This interface is used specifically for mass storage devices, in which the controller is integrated into the disk or CD-ROM drive.
A device controller is a part of a computer system that interprets the signals going to, and coming from the CPU processor. There are many device controllers in a computer system. Any device connected to the computer is connected by a plug and socket, and the socket is connected to a device controller. Device controllers play an important role in order to operate that device. It’s just like a bridge between the device and operating system.

Serial Advanced Technology Attachment (SATA)
This is a computer bus primarily designed for the transfer of data between a computer and mass storage devices such as hard disks drives and optical drives.
A computer bus (often simply called Bus) is a part of some computers used to transfer data, signals or power between some of the components that make up a computer

44
Q

Computer buses are used to:

A
  • Link between the CPU and on-board Memory.
  • Link between multiple CPUs in a multi-CPU system
  • Link the Arithmetic logic unit to the rest of the CPU
  • Connect hard drives, graphics cards, etc. to the main system.
  • Connect SATA, USB and Firewire.
45
Q

Storage Device, Storage capacity, Advantages & Disadvantages
USB drive

A

Capacity
Up to 256 GB

Advantages
* Easy to use
* Convenient (small size – can be placed in a pocket or on a key chain)
* Large storage capacity compared to diskettes
* Highly compatible - ‘plug and play’ (no software needed)
* Fast access, direct access
* Password protection
* Disk write protection switch (prevents data from being accidentally written over)

Disadvantages
* May not be easily read with computers using Windows 98 or older operating systems

46
Q

Units of storage:

A

bits, =1 bit
bytes, = 8 bits
kilobytes, = 1,024 bits
megabytes,
gigabytes,
terabytes
Petabyte
Exabyte
Zettabyte
Yottabyte

47
Q

what is a bit, byte, word, word size

A

A single ON or OFF signal (a single 1 or 0) ls called a bit. This is short for Binary Digit.

A byte is made up of a combination of 8 bits and has the capacity to represent one character i.e. a letter, a number, a symbol

A word is the number of bits the computer can process in one operation

A word size or word length is the number of bits in a word

48
Q

explain how the major hardware
components of a computer system
interrelate

A
49
Q

what is cloud storage and local storage

A

cloud storage involves stashing data on hardware in a remote physical location, which can be accessed from any device via instead of storing it on their own hard drives.

local storage involves storing data on physical hardware such as external drives and flash drives

50
Q

advantages of cloud storage

A

cost- purchasing physical storage can be expensive. without the need for hardware cloud storage is exceptionally cheaper per GB than using external drives

accessibility- using the cloud for storage gives you access to your files from anywhere that has an internet

Recovery- in the event of a hardware failure or other hardware malfunction, you can access your files on the cloud. it acts as a backup solution for your local storage on physical drives.

Advantages cont’d

Syncing and Updating- when you are working with cloud storage, every time you make changes to a file it will be synced and updating access all of your devices that you access that you access the cloud from.

Security- cloud storage providers and additional buyers of security to their since there are many people with files stored on the cloud, these providers go to added lengths to make sure your files don’t get accessed by someone who shouldn’t.

51
Q

disadvantages of cloud storage

A

internet connect- cloud based storage is dependent on having an internet connection. if you are on slow network you have issues accessing your storage. in event you find yourself somewhere without internet, you won’t be able to access your files.

Cost- there are additional costs for uploading and downloading files from the cloud. these can quickly add up if you are trying to access lots of files often.

Disadvantages cont’d

hardware drives

support- support for cloud isn’t the best, especially if you are using a free version of cloud provider. many providers refer you to a knowledge base or FAQs

privacy

52
Q

Advantages of local storage

A
53
Q

disadvantages of local storages

A
54
Q

Optical mark reader (OMR),

A

OMR detects the position of marks on paper. The marks must be made in pre-defined positions. The OMR detects the intensity of the light reflected from these marks. The computer records the position of the marks and analyses it determine the meaning of the data

OMRs are used for correcting multiple choice examinations, analyzing data from surveys, counting election ballots and validating lottery tickets.

55
Q

character readers MICR

A

MICR (Magnetic Ink Character Recognition) is used to read numbers on bank cheques. This input device works by detecting special magnetic ink

56
Q

advantages and disadvantage of MICR

A

Advantages of the MICR:
* Documents are difficult to forge
* Documents can still be read after being folded, soiled etc.

Disadvantages of the MICR:
* MICR readers are expensive
* The system can accept only a few characters

57
Q

character readers OCR

A

This is an optical scanner which utilizes special software to read characters from paper. The shapes of different characters are detected by shining light on them from a photo-electric device and sensing the patterns of reflected light. The reader software allows each character pattern to be compared with a set of stored patterns until the closest match is found. The match is then translated into text in the computer so that it can be manipulated by the user.

It is used in the legal service, postal service, utility and financial companies and by immigration officers at airports.

58
Q

advantages and disadvantages of OCR

A

Advantages of the OCR
* OCR is suitable for converting large volumes of printed data into electronic text on the computer so that it can be manipulated. It is great for archiving books, documents etc

Disadvantages of the OCR
* OCR has difficulty understanding handwritten text if the letters are not properly formed. OCR has difficulty recognizing unusual fonts.

59
Q

mouse

A

The mouse has a ball underneath, which rolls and determines the direction of the cursor, and buttons which allow the user to make selections.

In addition to moving the cursor, the mouse is used to select and open documents or programs, move icons from one place to another on the screen, select options from a menu, position the cursor when preparing and editing documents, and for drawing lines and sizing graphic objects such as pictures.

60
Q

joystick,

A

This device is used to control movement of the cursor or other objects on the screen by operating a small lever.

It is used mainly for playing games, but it is also used with scanners at hospitals.

61
Q

bar code reader,

A

Barcodes are read by a scanner in which a laser beam scans the barcode and the light is reflected back into the scanner. The information received by the scanner is sent for processing. Barcode readers give fast error-free data entry into the computer. It is a fast method of recording the sales of items.

Barcode readers are used in supermarkets, libraries, research, airports, postal services and warehouses.

62
Q

document scanner, (4types)

A
  1. Flatbed scanner: the picture is placed on a flat surface and the image is captured, similarly to how a photocopying machine works.
  2. Handheld scanner: the picture is read while the user drags the scanner over it. The quality of the image provided by this scanner is poor, but it is useful for quick data capture.
  3. Drum scanner: the document to be scanned is mounted on a glass cylinder. These are used in publishing industry (magazines, books) to capture images with high detail.
  4. Sheet-fed scanner: the sheet that contains the image is fed through rollers and the picture is scanned as the paper passes through.
63
Q

light-pen,

A

This is shaped like a pen and is connected to a VDU/monitor. It allows you to point and make selections more accurately on a screen. The tip of the light pen contains a light-sensitive element which, when placed against the screen, detects the light from the screen and enables the computer to identify the location of the pen on the screen. Making selections with a light is far more accurate than using your finger to make selections on a touch sensitive screen. They also allow you to draw directly on the screen.

However, they are not as accurate as a digitizing tablet and drawing can become uncomfortable.

64
Q

touch terminals,

A

A touch terminal, also known as a touch screen is a light-sensitive screen that detect when a person touches it, as well as the area of the screen that was touched. Various options are displayed on the screen and the user presses the one they want.

Touch screens are used on ATMs, microwave ovens, cash registers, at airports, fast-food outlets, theatre booking offices, etc.

65
Q

advantages and disadvantages of touch terminals

A

Advantages of the Touch Terminal
* The user can select the option very quickly.
* The user does not require any training to use it.
Disadvantages of the Touch Terminal
* The system is expensive.
* It is limited to certain applications.

66
Q

voice response unit,

A

This type of system requires the use of a microphone. It accepts the spoken word as input data or commands. The computer is programmed to recognize certain patterns of speech. The microphone is used to code human speech into a sequence of electronic signals. These signals are compared to a set of stored patterns. If they match, the command or data being entered is accepted by the computer and processed. Voice commands can be used to control machines or even enter documents in a word processor.

It is very useful for physically disabled persons.

67
Q

advantages and disadvantages of voice response unit

A

Advantages of the Voice Data Entry
* No typing is required
* The system can be used remotely e.g., by telephone

Disadvantages of the Voice Data Entry
* Recognition of words is still relatively slow since human speech can vary in tone and emphasis of various parts of words and phrases.
* The system is not suitable for use in noisy places.
* You may need to program (train) the system to understand your particular voice patterns.

68
Q

Touch Screens
(tablets),

A

This device looks like a small chalkboard. The tablet detects and transfers drawings made on it to the screen. The drawings are made with either a stylus (pen-like pointing device) or a puck (mouse-like device).

Graphics tablets are used by architects, mapmakers, artists and designers to create sketches and drawings on the computer.

69
Q

Touch Screens
(point of sale),

A

This is the combination of a barcode reader and computerized cash register. It is usually found in retail outlets. The barcode reader scans in information from the sale transaction and this is recorded in a centralized computer which is connected to the cash register. The information collected can also be used for stock control and sales analysis.

70
Q

advantages and disadvantages of Point of Scale

A

Advantages of the POS
* Customers get quicker and more accurate service, which improves efficiency.
* Supermarkets can get instant or continuous stock checks
* Saves on paper
Disadvantages of the POS
* Barcodes cannot be read by humans

71
Q

Touch Screens
(ATM),

A
72
Q

keyboard,

A

This device is used to enter text data or characters e.g., letters, symbols, numbers and commands specific to a program.

73
Q

digital camera,

A

This camera captures an image and stores it in memory within the camera. The camera has a sensor that converts the light into electrical charges. The processor in the camera converts this information into digital data and stores it on a flash RAM card. The digital images can then be uploaded from the camera to a computer where they can be displayed, manipulated or printed. The memory can be erased so that more images can be captured. Unlike normal RAM memory the RAM card is non-volatile. The resolution of the camera is measured in pixels. The more pixels a camera has the greater the detail captured.

74
Q

advantages and disadvantages of digital camera

A

Advantages of a Digital Camera
* Photos can be shown on a small screen on the camera, and resized and erased so that you can choose to store only the images that you want.

Disadvantages of a digital Camera
* It is relatively easy to lose or erase the camera’s memory card e.g., accidentally passing it through an airport x-ray machine.

75
Q

biometric systems,

A

Biometric refers to the science of identifying an individual through their body characteristics such as face geometry and hand geometry e.g., fingerprints, iris or retinal scans, vein and voice patterns. All these forms of identifying an individual can be input into a computer system set up for security purposes allowing access to buildings and bank accounts etc.

76
Q

sensors,

A

Chemical or physical changes in humans and their environment can be converted to electrical signals using sensors that pass data to a computer, where it is analyzed, stored and manipulated by specialized software. These sensors are useful in medicine, environmental planning and preservation, weather reporting etc. Sensors can be used to measure things such as heat, light, sound, pressure, strain, acidity(pH), oxygen concentration, humidity, pulse, water level, water flow, speed, tilt or even a door or valve opening or closing.

77
Q

remote control,

A

A remote control emits a beam of infra-red light that carries data signals. They are used to input data to televisions, stereo systems, VCRs, DVD players and by computers as a wireless means of communication.

78
Q

sound capture,

A

Microphones are used for sound capture. All modern computers contain built-in microphones and sound cards to allow voice or music to be recorded. The sound card digitizes the data into a form that the computer can understand.

79
Q

pointing devices,

A

These devices are used by graphical operating systems such as Windows to show the movement of the pointer or the cursor, and enable the control and selection of objects on the display screen.

This group of devices includes the mouse, trackball, pointing stick, touchpad, joystick, light pen, digitizing tablet and touch screen.

80
Q

webcam.

A

A webcam is a video capture device connected to a computer or computer network, often using a USB port or, if connected to a network, Ethernet or Wi-Fi. Their most popular use is for video telephony, permitting a computer to act as a videophone or video conferencing station. This camera is used to record and edit video images (i.e., moving or still images). The images are stored in a format that can be displayed on a web page. Web cams are used in video conferencing.

It is also useful in security surveillance.

81
Q

human readable and machine readable

A

If the output can be read by human beings it is said to be human readable. If the output cannot be understood by humans it is said to be machine readable.

82
Q

two types of output

A

Softcopy output is temporary output e.g., information displayed on a screen or in voice or audio form through speakers. This kind of output disappears when the computer is switched off since the screen or the speakers need the computer to work.

Hardcopy output is permanent output e.g., information printed onto paper or film. It is tangible – you can hold it in your hands.

83
Q

Monitors,

A
84
Q

One way of classifying printers is as: character, line and page printers

A
  • Character printers: these print one character at a time similar to a typewriter. They are slow.
  • Line printers: They print a line at a time. Multiple hammer-like keys forming a line of text hit the page at one time. They are much faster than character printers and are used to print large volumes. They print a limited number of characters and do not print graphics.
  • Page printers: these print a whole page at a time. They are therefore even faster and deal with very large volumes of printed output.
85
Q

classifying printers is as:
1. Impact printers
2. Non-impact printers

A

Impact printers use a printing mechanism called a print head. They make their output by pressing the print head against a ribbon, which then hits the paper.

Non-impact printers are faster, quieter and produce better quality print than impact printers. Unlike the impact printer, the printing mechanism makes no contact with the paper.

86
Q

types of impact printers & non impact printers

A

The main types of impact printers are dot matrix, daisy wheel and drum, chain or band printers.

The main types of non-impact printers are laser printers, inkjet printers and thermal printers.

87
Q

dot matrix (character printer)

A

Characteristics:
* Characters are formed from a matrix of dots.
* The speed is usually 30 – 550 characters per second (cps)
* It is very noisy
* It is relatively fast
* The print obtained is usually poor.
* They are useful for low-quality carbon copy prints or printing on continuous sheets of paper e.g., invoices (bills).
* They are not good for printing shaded graphics or photographs.

88
Q

Daisey wheel (character printer)

A

Characteristics:
* It is very noisy
* Printing is slow (less than 90 cps).
* The text is generally crisp and clean.
* The size and font produced can only be changed by using a different daisy, as the characters on the wheel are fixed.

89
Q

Drum, chain or band printer (line printers)

A

Characteristics:
* They are fast (2500 lines per minute.
* They are used to print large volumes of information.

90
Q

Thermal printers (character printers)
There are two types of thermal printers:

A
  • Direct Thermal printer: this printer uses heated pins to form the characters. These pins come into contact with special heat-sensitive paper to form darkened dots when the pins reached a specific temperature, thus shaping the characters. The pins actually burn the dots into the specially coated paper. Exposure to sunlight and heat tends to darken the thermal paper. The print quality is poor.
  • Thermal wax transfer printer: the print head of this printer melts a wax-based ink from a transfer ribbon onto paper. This printer does not require special paper. Thermal printers are used in portable calculators, fax machines and some ATMs (automated teller machines).
91
Q

Inkjet printers (line printers)

A

Inkjet printers (line printers)
Inkjet printers produce their output by spraying small droplets of ink at high speed into paper, in a pattern. These printers can print in both black-and-white and colour. They used at home and small offices. The print quality is good but not as good as the laser printer. Inkjet printers can also produce both text and graphics. They are cheaper than laser printers.

92
Q

Laser printers (page printers)

A

Laser printers (page printers)
These use a process similar to that of a photocopying machine. They are used in large companies or institutions such as schools. They can also be found in modern offices. A laser beam and dry powdered ink called toner produces a very fine dot matrix pattern. This pattern is transferred to the page and then fused onto it by heat and pressure. These printers can print in black and white or colour. These printers can produce more than 40 pages per minute (ppm). The print quality is very good. Laser printers produce both text and graphics. They are very expensive.

93
Q

Printers ( 3D Printers)

A
94
Q

Printers (plotters)

A

Plotters use different printing processes e.g., some work like an inkjet printer and others use the same method as laser printers. They are used to produce documents with high quality graphics in a variety of colours e.g., maps, architectural drawings and charts. They can print on large sheets of paper.

95
Q

There are three main types of plotters:

A

There are three main types of plotters:
* Pen plotters: these use a mechanical arm or rail that holds a pen which can be moved across the page.
* Inkjet plotters: these work in the same way as inkjet printers by spraying ink onto the paper.
* Electrostatic plotters: these work in the same way as laser printers

96
Q

microfilm

A

COM (Computer Output on Microfilm/Microfiche)

COM is a method that is used to store computer documents by reducing them in size to fit on very small photographic sheets of film. They are used to store large volumes of data. These sheets can be read using a special magnifying machine. Microfilm is a roll of film and microfiche is a rectangular sheet of film on which many frames/pages of information can be stored.

information technology (8 decks)

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