Transcript Input devices

Bits and Bytes!
Concepts of
ICT
explained
MACalvey/Teachnet/Bits& Bytes
2005
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A computer..?
• Job specification? Desktop publishing,
video editing, sound editor, internet
browser, calculates wages......
OUTPUT
INPUT
PROCESSES
A computer accepts Input, Processes it in some way,
then displays or outputs the information.
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Types of Computers
Mainframe:
• Expensive with large storage capacity
• Can cope with very high volumes of transactions
• Typically used by banks, insurance companies,
government organizations and large corporations
• Hold vast databases of information which can be accessed
quickly and updated by a large number of users at the same
time and support a large number of peripherals
• Expected to run 24 hours a day, 365 days a year
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The PC/ Personal Computer
• Types: Desktop/*Laptop or Notebook/ Personal Digital
Assistants (PDAs)/Palmtop computers
• * Laptop - Portable/Own integral screen and
keyboard/May have own rechargeable batteries or require
electric power
• Main uses of PC’s are as desk-top business computers used
for word processing, small business accounts, financial
planning, or as home computers.
• Capable of stand alone or networked use, possible to link
PC’s together to share storage facilities, printers, or files of
information.
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Network server: Administers, supports and
protects security of a computer network
Dumb Terminal
- An input or output device with no
processing power of it’s own,
Consists of a keyboard, display screen and a
communication link to a mainframe computer.
Accepts input from user, displays results, processing done
by server.
Intelligent terminal
- a terminal which retains a
program and allows processing of data to be carried out
without further access to the host computer.
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Hardware
The physical components that make up a
computer system
Includes
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monitor,
keyboard,
cables,
memory,
printer and the case containing the computer itself (the
processor)
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Software
Term used to describe the sets of instructions or
programs that tell the hardware what to do and
includes the programs which we use on the
computer e.g. Word processing, games,
encyclopedia
Two types of Software:
– System Software
– Application Software
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System software
• Manages files and storage, Controls devices,
Recognizes input, Sends output to screen, Communicates
with peripherals
• Main piece of systems software is the OPERATING
SYSTEM.
• Operating systems include DOS, UNIX, Windows 3.1, 95,
98, 2000, XP.
DRIVERS : Special piece of software to enable operating
system to control hardware e.g. Certain printers require
separate drivers, compatible with current operating
system, to be installed before printer will work.
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OPERATING SYSTEM
Automatically loads when computer is
switched on, otherwise computer will not work.
Functions
• Boots up the system , controls input and output devices,
manages the transmission of data between application
software, storage device and RAM.
• Translates commands received from the applications
software: word processing programs, spreadsheets etc into
instructions specific to the hardware
• Distributing RAM, controlling input and output devices,
allowing/preventing access to authorised/unauthorised
users
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APPLICATION SOFTWARE
Generally Applies To Programs Written For A Particular
purpose e.g. Word, Excel, Powerpoint, Access,
Desktop publishing
WORD PROCESSING
SPREADSHEETS
• A programme specifically
developed for the typing and
production of letters, reports
and documents.
• Unlike typewriter, text can be
saved and modified.
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Microsoft Excel - Commonly used
spreadsheet
Excel workbooks - contains
the file in which work is done and data
stored
Each workbook contains many worksheets
Each spreadsheet consists of columns
down and rows across.
Spreadsheets - largely are used for
calculations from simple additions to
complicated formulae
Graph feature - range of options used for
comparisons of data
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DESKTOP PUBLISHING
• A Programme for producing professional-quality
reports, booklets and magazines.
Publisher provides pre-designed templates for a wide range of documents: newsletters,
cards, banners, flyers, brochures, calendars, advertisements.
Templates can be modified or the user can create from scratch.
MICROSOFT ACCESS
•A program that enables creation of and working of databases
MICROSOFT POWERPOINT
•A program that creates visual slides for a presentation and
handouts for use when addressing an audience
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Memory
• RAM (Random Access Memory)
• ROM (Read Only Memory)
• Cache Memory
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Random Access Memory(RAM)
• RAM is temporary, fast memory
• Working memory - holds lists if instructions that it is currently
working on and handles work since last saved
• RAM is volatile and requires a constant supply of electric power , data
is lost when the power to the computer is turned off
• Saving work removes it permanently from RAM to disk
• Additional RAM chips can be added by installing a memory-expansion
card
• The more RAM, the faster the computer operates, the more programs
that can be open simultaneously and the faster they perform
• A certain minimum RAM is required to install and run programs
• 64 Mb or 128Mb RAM minimum now required to run most programs
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ROM (Read Only Memory)
• A memory that holds data or special instructions for computer
operation, such as starting the computer or putting characters on the
screen.
• Contents of ROM are permanently fixed when the computer chip is
made
• Information in ROM remains intact even when computer is switched
off
• Computer can only “read” what is in ROM, it cannot alter it
•
ROM cannot be altered by the computer or programmer - the actual
content of ROM is fixed at the time of it’s manufacture. ROM can only
be changed by changing the computer.
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Cache memory
• A special high-speed memory area linked to the processor
that the CPU can access quickly.
• Frequently used data is stored here saving the processor
from having to read from the hard disk all the time. Allows
the CPU to run faster because it doesn’t have to take time
to swap instructions in and out of RAM.
• Measured in bytes ranging 128kB - 512kB
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Other forms of memory
• Video RAM (VRAM) used to store display images for the
monitor.
• Determines how fast images appear and how many colours
are available.
• Video memory chips are essential when running programs
that display a lot of graphics.
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Memory Measurement
• Bit: Short for Binary Digit-the smallest unit of Data that
the computer can handle. Data is represented by on and off
states of the computers electronic circuitry.The binary digit for on is 0
and off is 1.
• Character: Combination of bits(0s and 1s) are used to represent
characters:letters,digits and special symbols like:$, % etc.
• Byte: A fixed number of adjacent bits that represent characters are
called a byte-this is the amount of memory needed to store one
character such as a letter or a number.Eight bits are used to represent a
character.
• Field: A collection of related characters.
• Record: A collection of fields that relate to a single unit is a record.
• File: A grouping of related records
• Kilobytes: equal to 1024 bytes or characters (KB)
• Megabytes: equal to 1024 kilobytes (approx. one million bytes (MB))
• Gigabytes: equal to one billion bytes (GB)
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Computer Power
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CPU Speed
The amount of RAM
Cache memory
Hard disk size
Clock speed
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C.P.U.
• The central processing unit is the little chip
in personal computers that controls
everything.
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Hard Disks
• Enable large amounts of data to be stored
accessed, and read at very high speeds
• Consists of magnetic storage plates encased in a hard disk
drive
• The computer’s main storage device holding the files for
the operating system plus the program and data files
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The System Clock
• Every microprocessor contains a system
clock.Controls how fast the operations
within a computer take place.
• Processing speeds are expressed in
megahertz(MHz)
• The higher the MHZ speed - the faster the
computer
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Systems Software Utilities
• Utilities are programs that are designed to
assist with the routine tasks of running a
computer system
• Examples- programs to copy or delete files,
rename files, and format new disks
• Text editors (used to write and amend
programs) and debuggers (used for finding
errors in programs) also available.
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Graphical User Interface (GUI)
• Incorporates four elements: Windows, Icons, Menus
and a Pointing Device
• Apple Macintosh Finder or Microsoft Window use a
computerised desktop as the interface between the user
and the operating system. Pictures or icons represent such
items as disks, files and programs. A GUI has pull-down
menus that allow the user to select from a predefined list of
command choices. A GUI uses a mouse to allow the user to
point at and select the items or commands that are required.
• GUI is easy to use icons are self-explanatory; a lot of
similarity between basic functions of all Windows-based
software.
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Data - Stages
3 stages:
Input
Processing
Output
• Input: Data is input into the computer by typing on a keyboard or
using a scanning device such as a barcode reader in a supermarket
• Processing: Once data is input it is processed in the “brains” of the
computer- (Central Processing Unit)
• Output: Data can be distributed to users via Soft Copy or Hard Copy
Soft Copy - Temporary, Displayed on monitor, Information vanishes
once monitor is turned off
Hard Copy - Permanent, Printed copy on paper, acetate or microfilm
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Input devices
Inputting methods have evolved dramatically over the years
from the earlier use of keyboard, punched cards and paper tape.
Input methods include:
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The keyboard
The mouse
Trackerball
Scanner
Touchpad
Light Pen
Joystick
Voice Input
Graphics pad
Magnetic disk and tape input
• Document readers
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Web Cam
Digital camera
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Keyboard is the slowest
means of input
• Most used input device
• Its familiar
• Easy to operate
Mouse
• Many different types including
cordless
• Gives fine conrol over use of
applications
• Access to menus on
Rightclicking
Tracker ball (track ball)
• A pointing device which you
rotate to move the mouse
cursor; commonly found on
notebook computers
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Scanners
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Scanner - used as a means of capturing an existing two-dimensional image - a
drawing or a photograph that could not be input using a graphics
pad
image scanners divide a picture into a matrix of tiny dots each of which is stored in
a file in the computer.
It is then possible to use this file with an existing text file in order to combine
pictures with text as in a newspaper
Optical Character Recognition (OCR)
• Enables information to be automatically “read” from a printed document
• OCR scanners can recognise typed and neatly handwritten material.
• OCR is used by organisations like gas, electricity and credit card companies,
all of whom need to process large numbers of similar documents in a short
space of time.
Video scanners
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The video scanner uses a video camera to capture an image for processing either of an existing
two-dimensional picture or of a three dimensinal object
Video scanners will generally offer a higher resolution than image scanners
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Touch screens (touch pads)
• Designed to avoid the use of a computer keyboard, the user
will simply touch the appropriate icon or other reference on
the screen.
• Action will be sensed by the computer, and the option chosen
will be acted upon.
Light Pens
• Device used in conjunction with special hardware and
software that shines light on to a VDU screen to indicate a
choice from a menu or to input a location in graphics work
• In libraries, bar codes are read by using a light pen or wand
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Joysticks
• Input device for a microcomputer.The
stick as it moves (usually in one of
eight directions) is able to control the
movement of a shape on the screen.
Sometimes there are 2 joysticks
enabling a screen game to be played
by 2 players.
Voice Input
• Possible to programme a computer to
respond to voice commands
• Present voice recognition systems need
to be “trained” to cope with a particular
voice
• Must be restrained if the user gets a
cold or has a sore throat
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Graphics pad
• Used to input graphic image to a computer
• Freehand images can be input by drawing with the stylus
on the bed of the pad.
• Existing drawings may be traced by the stylus on the bed; alternatively
they may be input by using a cursor similar to a mouse
• The cursor is positioned in turn over the key points on the drawing and
one of the buttons on it is pressed
• The computer records these points and joins them together as
necessary to define the computer image.
• When used to input existing drawings, graphics pads may also be
called digitisers.
• They are used by architects to design buildings, and as part of CAD
systems in engineering
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Magnetic disk and tape input
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Both widely used for the storage of computerised information
A computer storage device that looks rather like an LP record that has the same
magnetic coating as an audio
Information is recorded onto and read from the surface of the disk in much the same
way as a domestic cassette tape recorder is used to record and play back music
Magnetic tape is the computer equivalent of the reel-to-reel tapes found on professional
tape recorders
Data can be transferred from magnetic disk or tape far faster than it can be input from
any other device
Speeds of input from magnetic tape or disk are termed data transfer rates
Magnetic ink character recognition (MICR)
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Enable the fast and efficient clearing of cheques
Characters are printed in a special ink that can be magnetised to give off a
unique magnetic field that enables each character to be read
Used by the banks as a way of speeding up the cheque clearing system- input
speeds can be anything up to 2000 cheques a minute
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Card Readers
• A device that reads information held in the form of
a magnetic strip on a plastic card e.g. Credit card,
ATM card
Bar-code readers:
• An arrangement of vertical bars and spaces that can be read by an optical
scanner and used as a means of identifying products or stock items
• Seen on most products purchased in supermarkets, inside library books, and on
such items as freezers and computers. In supermarkets, each product carries a
unique bar code that can be used both to calculate the size of the bill at the
point-of-sale (POS) terminals (or check-outs) and for stock control.
• System operates from a central computer which controls the POS terminals.
• When shoppers goes through a check-out, each item is passed over the scanner
which reads the bar code and refers to the central computer for the description
and price.
• Information is relayed to the check-out, where it is displayed on a customer
panel printed on a receipt. Stock level for the item purchased will be reduced ,
providing management with up-to-date stock information and enabling more
efficient stock control and ordering.
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Document readers
• Can be read by humans as well as by machines
• Used where there is a need to be able to process large volumes of
similar documents, like cheques or gas bills Automated processing of
cheques quickly
• Computer marking of multiple choice answer sheets
• Reading of large volumes of credit card payment slips
Web Cams
• Allows two way communication including sound and video as well as
text
Digital cameras
• Images are stored digitally in memory in camera
• Pictures can be transferred to computer and edited digitally
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Computer Output
Output: Once the data has been processed, information can
be distributed to users.
• Computer output can take the form of a display on a screen,
a print-out, or transfer of information on to a magnetic tape or disk.
Most output falls into one of two categories: hard copy or soft copy.
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Hard copy is output in a permanent or touchable
form e.g. printed form such as on paper or microfilm. May
be produced either on separate sheets or on continuous
stationary taking the form of folded and perforated lengths
of paper
Soft copy is information that is displayed visually on a screen
or monitor - temporary: once the monitor is turned off or
new information is required, the old information vanishes.
Also can be in audio form, as in speech or music
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Visual output
• Most common form of soft-copy output is information
displayed on a screen or cathode-ray tube(CRT)
• The VDU enables a user to input information to a
computer by using a keyboard, mouse or touch screen
facilities and to view output on a CRT
• Two factors limit the use of the CRT; its weight and the
amount of power it consumes
• Liquid-crystal displays (LCDs) similar to those found on
some digital watches are both light and economical enough
to be widely used for portable computers
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Computer output on microfilm
(COM)
• As an alternative to printed output, another form of hard
copy is computer output on microfilm or microfiche
• COM is the recording of what would otherwise be printed
output direct in reduced form on to either rolls or sheets of
photographic film
• Microform can store documentary information with textual
and graphical content
• Structure can be either microfilm (a continuous reel) or
microfiche (a grid pattern)
• Microform reduces storage space requirements by
approximately 95% of that required by paper
documentation
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Audio output
Covers the range from the simple ‘beep’ to full speech
synthesis.
Speech synthesis is the production of a sound
corresponding to spoken words and it is of great use
where a user is unable to look at a CRT or is occupied
with another.
Computer Speakers
Have the same function as hi-fi music speakers used in
the home stereo systems.
Differ from conventional speakers in that they are self
amplified and magnetically shielded.
Most speakers are AC powered and have separate volume
tone controls.
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Printers
Two most common types of printers
• Inkjet Printers
• Laser Printers
*Also third category - Matrix Printers
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Ink-jet printers
• Work by using tiny jets to spray ink at high speed onto the
paper
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Forms characters by projecting the ink from the small ink nozzles (the same
way as by the dot-matrix printer) on to the paper - for this reason are termed a
non-impact printer.
Ideal for low volume printing with high quality where speed is not priority
Major advantage over a dot-matrix printer is low level of noise
Laser printers
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Shares the same image-printer technology as the photocopier.
Print image is produced by a laser beam which scan across the print drum, line
for line as the print cylinder rotates.
High quality at high speed
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Dot-matrix printers
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Gets name from way in which a number of needles in the print head are used
to print text as a series of dots using a carbon ribbon.
The more pins the print head has, the higher the quality of print
The speed at which a dot-matrix printer is able to operates depends on which
typeface is being printed
Typical speeds may range between 40 and 500 c.p.s according to the print
quality.
Noisy and not high quality
Suitable for high volume/low quality printing e.g. printing company payslips
Widely used as a micro-computer peripheral
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Thermal printers
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Use heat to transfer the image from the print head to the paper.
Text and images are made up from a series of dots, in common with
other matrix printers, but with this process the print head may be either a fixed array of
thermal elements
Daisy-wheel printers
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This printer takes its name from a flat disc with a number of stalks or petals radiating
from its centre each of which has a character at its tip.
Daisy wheel rotates at high speed and the petals are pushed on to a ribbon which, in turn
transfers the characters to the paper.
Line printer
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Gets its name from the way in which it prints a line of text at a time.
Two types- chain printer and the drum printer.
Main feature is their speed, the fastest printing text at around 5000 lines per minute.
This is achieved by hitting the paper against the character and printer ribbon.
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Graph plotters
• An output device similar to a printer but normally
allows printing of larger images
• The graph plotter is a specialist device designed to produce
high-quality pictures and designs.
• Unlike matrix printers, a graph plotter reproduces the
human action of drawing by using a pen.
• Widely used by architects and designers of all kinds
• Two types of graph plotter- flatbed and drum
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Peripherals
A Peripheral is any device that is connected to and controlled
by a computer but external to the CPU etc.
Peripherals include:
• Printers
• Loudspeakers
• Scanners
• Digital camera
• Microphone
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Storage
Primary and Secondary Storage:
• The Term primary storage (main memory) refers to RAM
• Secondary storage is auxiliary storage - any storage device
designed to retain data and instructions (programmes) in a
relatively permanent form.
• Secondary storage is non-volatile, meaning that saved data
and instructions remain intact when the computer is turned
off.
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CD-ROM
Compact Disk Read Only Memory
• Widely used for reference material and training purposes, has huge
storage capacity
• Ideal for storing all forms of images including video sequences which
take large amounts of storage space
• Not used for storage of documents which require regular updating.
• Speed of CD ROM drive is regularly being improved
• Standard CD-ROMS can only be written to once, CD-RW disks can be
written to more than once
• A CD-writers/burner used to record or copy to a CD
• CD-ROMS now being over taken by DVDs (Digital Versatile Disks)
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Diskettes
• A diskette or floppy disk stores data and programs as magnetised spots
• The disk is contained in a plastic case to protect it
• Diskettes are sometimes called “floppy” because the disk within the
envelope or case is flexible, not rigid.
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Zip Disk/Zip Drive:
• A removable disk, capacity of 100 - 250 MB
• Can be internal or external
• Popular for keeping backups and for
transferring large files between computers
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Electronic Commerce
E-Commerce a generic term for all forms of business
transactions on the Internet. The potential to advertise and sell ones
`product` via a web site to mass audiences has limitless appeal.
• The 7 most popular buys on-line are: Books, CDs, Travel, Music,
Electronics, Computer hardware and Clothing. Books sales on-line
phenomenal growth eg. Amazon.com. CDs from America half the local
price; however, delivery cost must be considered.
• lastminute.com specialise not only in cheap travel but also in
occasional purchases like cars or mobile phones.
• Shopping on-line using a credit card is relatively safe. It is advisable to
use e-commerce sites that keep your card details on a secure server so
you don’t have to send them each time you make a purchase. Ensure
that your browser is set up for secure connections to the internet. A
padlock displaying on the status bar of the program when you connect
to a secure server indicates that your data is secure.
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Requirements for connecting a
Computer to the internet
• A computer with a fast processor, 16-128MB of RAM, up
to 100MB of free hard disk.
• A Modem (unless broadband is available)
• A Telephone line
• An Internet Service Provider (ISP). Modem via the
telephone line will link to the internet through the
computer system of the service provider.
• Connection Software
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Data Protection Act 1984
• Safeguard the privacy of the individual
• Legislation protects personal data handled in computers
• Aim to control the immense potential for misuse of
information that arises when personal data is stored in
computers.
- Once data has been transcribed from paper files into a form
that is easily readable and accessible by computers, it is an
inexpensive and easy task for the data to be extracted from
one record and correlated with personal data concerning
the same person from another file - infringement of
privacy.
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Requirements of organisations that maintain
personal records on computers:
• To declare and/or register the use for which data is stored
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Must make information available to those authorised to receive without undue
delay or inefficiency
• Provide the data subject with a right of access to data concerning
himself on their computer
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Keep information secret from those not so authorised in such a way that the
cost of unauthorised disclosure would exceed the value of the information to
the illegitimate recipient.
• Maintain a prescribed minimum level of electronic and physical
security in their computer installations - System may involve physical
security (safes, locks entry cards) for access to disks and passwords and also
the technique of cryptography and authentication.
• Not to transmit personal data to any organisation that does not have
similar controls over misuse of data
• The OECDS has also drafted a convention of similar effects
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Repetitive strain injury (RSI):
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Also known as repetitive motion injury and cumulative trauma disorder is
the name given to a number of injuries resulting from fast, repetitive work
RSI causes neck, wrist, hand, and arm pain.
RSI problems can result from prolonged computer keyboard use
An RSI called carpal tunnel syndrome is particularly common among young
people who use computers and certain types of scanners intensively. This
syndrome involves damage to nerves and tendons in the hands.
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RSI Causes:
• Repetition and duration: Prolonged, constant and
repetitious movements such as typing irritate
tendons and nerve casings, causing them to swell.
• Force: The harder you hit the keys, the more likely to suffer
injury.
• Joint angle: Flexing raising, or twisting hands to reach the keys
constricts the carpal tunnel.
• Prolonged constrained posture: Holding any position without
moving puts excessive strain on muscles and tendons.
• Left untreated, this syndrome can cause atrophied nerve damage.
To avoid RSI:
• Frequent short rest breaks.
• Plenty of sleep and exercise, maintain appropriate weight, sit up straight and
learn stress- management techniques.
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Health and Safety: Computer work environment
• Prolonged use of computers can cause eyestrain,muscular
strain, changes in colour perception, back and neck
pain,stomach aches, and nausea.
• To reduce such physical problems,time spent at a VDU be
reduced to a maximum of two hours per day of continuous
screen work.
• Periodic rest breaks be granted.
• Steps taken to reduce or alleviate glare produced by
overhead fluorescent lighting-glare reduction screens
should be available as required by the employee.
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Systems Development
Process by which a computerised information system is created
• Stage 1: choosing the information system to be
computerised
• Stage 2: Feasibility study
• Stage 3: Full analysis of the system to be computerised
• Stage 4: Designing how the computerised system will work
• Stage 5: Writing the programs
• Stage 6: Implementing the new system
• Stage 7: Maintaining the System
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Computer networks
Connecting a computer to other computers in same
building or in another part of the world
• Share Hardware eg. Printers
• File - Sharing
• E-mail / Data exchange
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Computer Based Training (CBT)
Advantages
• Flexibility of studying whenever
• Can work at own pace
Disadvantages
• No regular routine
• Student needs to be strongly motivated or highly
disciplined
• Cannot consult a tutor
• No interaction with other students
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Multimedia
• Global term for the developing computer technology that
can combine text, graphics, hi-fi sound, animation, and
full motion video in a single high-resolution display
•
Made possible by the common use of digital recording of text,
graphics, sound, and video, coupled with the increased
processor speeds required to handle large video files
Multimedia Applications
• Training: Cheaper alternative to traditional techniques for staff induction,
training in new procedures and general management training
• Architectural Visualisations: CAD system
• Advertising/promotions Logos, trademarks, and storyboard outlining:
Advertising can be created, animated, and given a sound track using
multimedia authoring software
• Home Entertainment: include interactive cartoons, games, and an interactive
multimedia world atlas
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E-MAIL
Advantages
Disadvantages
• Carries of viruses
Quick inexpensive
immediate contact can be
• Unsolicited e-mails: Spam
made
• Using the cc or bcc facility
numerous communications
can be distributed
simultaneously
• Attachment facility provides
the means of forwarding
long files
•
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Viruses
• A virus is a program code written to replicate
by attaching copies of itself to other objects within the
system, normally also having a detrimental effect. Usually
lie dormant for a while, then establish their presence by
displaying a message, stopping the computer or deleting a
file.
• These destructive programs infect a computer similar to
the way biological viruses infect people.
• Problems may range from displaying messages through
loss of service to corruption or complete destruction of
data
• A program virus will seek out and copy itself into other
program files whenever a previously infected program is
run.
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Virus Protection
• To protect, purchase your software only from reputable
dealers
• Run an anti-virus utility and back up hard drive
• Greatest carriers of viruses are disks which are illegally
copied programs, especially games
Backup
• A copy you make of a file in case the original file gets
destroyed or corrupted
• Use backup command of your computer
• Can back up files to floppy disks, a tape drive etc
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Precautions and power failure
• Use special anti-power surge extension leads on
all computer sockets
• Use UPS (Un-interruptible Power Supply)
• Have backup of files
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