Transcript Introduction to Computers

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Computers are showing up everywhere you
look, and even in places you can't see.
Computers check out your groceries, pump
your gas, dispense money at the ATM, turn
the heat on and off, control the way your
car runs. They're everywhere!
A computer is an electronic device that executes the
instructions in a program.
Modern computers are electronic and digital.
A computer has four functions:
a. Accepts data
Input
b. Processes data
c. Produces output
d. stores results
Processing
Output
Storage
All computer systems perform the following five basic
operations: Inputting:
The process of entering data and instructions into
the computer system.
 Storing:
Saving data and instructions to make them readily
available for additional processing, as when required.
 Processing:
Performing arithmetic operations (add, subtract,
multiply, divide, etc), or logical operations on data, to
convert them into useful information.
 Outputting:
The process of producing useful information or
results for the user, such as a printed report or visual
display
 Controlling:
Directing the manner and sequence in which all of
the above operations are performed.
Input Unit :
- It accepts or reads the instructions and data from the outside world
- It converts these instructions and data in computer acceptable form.
- It supplies the converted instructions and data to the computer system for
further processing.
Output Unit :
- It accepts the results produced by the computer, which are in coded form,
and hence, cannot be easily understood by us.
- It converts these coded results to human acceptable (readable) form.
- It supplies the converted results to the outside world.
Memory Unit:
- Memory unit are to store the data and instructions required for processing
- They are to hold the final results of processing, before these results are
released to an output device
The Memory unit is comprised of the following 2 types of storage:
Primary storage
Secondary storage
Arithmetic Logic Unit:
 The arithmetic logic unit (ALU) of a computer system is the
place, where the actual execution of the instructions takes
place, during the processing operation.
 ALU’s are designed to perform the arithmetic operations (add,
subtract, multiply & divide) and logical operations or
comparisons.
Control Unit
 The control unit acts as a central nervous system, for other
components of the computer system.
 It manages and coordinated the entire computer system
Central processing unit (CPU):
 The control unit and ALU of a computer are jointly known as
the Central Processing Unit
 The CPU is the brain of a computer system & all calculations
and comparisons are made inside the CPU.
 CPU is responsible for activating and controlling the
operations of other units of the computer system.
A microprocessor -- also known as a CPU or
central processing unit -- is a complete
computation engine that is fabricated on a
single chip.
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Using its ALU (Arithmetic/Logic Unit), a
microprocessor can perform mathematical
operations like addition, subtraction,
multiplication
and division.
A microprocessor can move data from one
memory location to another.
A microprocessor can make decisions and jump to
a new set of instructions based on those
decisions.
Hardware:
the physical parts of the computer.
Software:
the programs (instructions) that tell the
computer what to do
Data:
individual facts like first name, price, quantity
ordered
Information:
data which has been massaged into a useful
form, like a complete mailing address
Default:
the original settings; what will happen if you
don't change anything.
Input
The input hardware allows you to enter data into the computer. The primary
devices used are the keyboard and mouse.
Keyboard –
The keyboard looks like the typewriter. A numeric keypad is located to
the right of the keyboard.
Mouse –
The mouse is a device that allows you to control the movement of the
insertion point on the screen.
There are other input devices, such as touch screen, joystick, modem,
scanner, and voice recognition systems.
Touch Screen:
A display screen that is sensitive to the touch of a finger or
stylus. Touch screens are very resistant to harsh environments
where keyboards might eventually fail.
Joy Stick:
A pointing device used to move an object on screen in any
direction. Joy sticks are used extensively in video games and in
some CAD systems
Light Pen:
A light-sensitive stylus wired to a video terminal used to
draw pictures or select menu options. The user brings the pen to
the desired point on screen and presses the pen button to make
contact
Processing
The central processing unit or (CPU) is the "brain" of your computer. It
contains the electronic circuits that cause the computer to follow
instructions from ROM (read only memory) or from a program in RAM
(random access memory).
CPU contains three parts.
1. Arithmetic Logic Unit –
ALU is where the "intelligence" of the computer is located. It can
add and compare numbers.
2. Memory –
Memory contained on a chip are
 Primary Memory
Primary Memory:
It is also known as main memory, is used to hold
pieces of program instructions and data.
It is of 2 types:-
RAM (Random Access Memory)
ROM (Read Only Memory).
–ROM memory has been installed on your computer by the
manufacturer and can not be altered.
–ROM determines all the basic functions of the operation of
your machine, such as startup, shut down, and placing a
character on the screen.
–RAM is temporary memory, which displays the
information you are working on.
–RAM remembers what you see on your screen while you
are working.
–Today's applications required large amounts of temporary
memory, which may require you to upgrade and add
more RAM memory.
3. Control Unit –
This is the part of the unit, which directs information
to the proper places in your computer, such as
calculation of information by the ALU unit or to store and
print material.
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Short for programmable read-only memory, a
memory chip on which data can be written
only once. Once a program has been written
onto a PROM, it remains there forever.
Unlike RAM, PROMs retain their contents when
the computer is turned off.
The difference between a PROM and a ROM
(read-only memory) is that a PROM is
manufactured as blank memory, whereas a
ROM is programmed during the manufacturing
process.
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To write data onto a PROM chip, you need a
special device called a PROM programmer or
PROM burner. The process of programming a
PROM is sometimes called burning the PROM.
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An EPROM (erasable programmable read-only
memory) is a special type of PROM that can be
erased by exposing it to ultraviolet light. Once it
is erased, it can be reprogrammed. An EEPROM is
similar to a PROM, but requires only electricity to
be erased.
What is an EEPROM?
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Pronounced double-ee-prom or e-e-prom, short for
electrically erasable programmable read-only memory.
EEPROM is a special type of PROM that can be erased by
exposing it to an electrical charge.
Like other types of PROM, EEPROM retains its contents
even when the power is turned off. Also like other types
of ROM, EEPROM is not as fast as RAM. EEPROM is similar
to flash memory (sometimes called flash EEPROM).
The principal difference is that EEPROM requires data to
be written or erased one byte at a time whereas flash
memory allows data to be written or erased in blocks.
This makes flash memory faster.
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Very fast memory used to improve the speed of a computer,
doubling it in some cases
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Acts as an intermediate store between the CPU and main
memory
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Stores the most frequently or recently used instructions and
data for rapid retrieval
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Generally between 1Kb and 512Kb
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Much more expensive than normal RAM
Memory Cache speeds up a computer by storing data the
computer has recently used.
There are 2 types : Internal & External
External Cache
If the computer cannot find what
it needs in the Internal Cache, it
looks in the external cache. This
is usually located on the
Motherboard. In some CPU chips
the External cache is built in.
Internal Cache
When the computer needs
data it first looks in the
Internal cache. This is
located on the CPU chip and
provides the fastest way for
the computer to get data.
Virtual memory
Space on a hard disk
used to temporarily store
data and swap it in and
out of RAM as needed.
Motherboard
This is the main circuit board that all of the other
internal components connect to.
The CPU and memory are usually on the
motherboard. Other systems may be found directly on
the motherboard or connected to it through a
secondary connection.
For example, a sound card can be built into the
motherboard or connected through PCI (Peripheral
Component Interface).
Output
Output devices such as a monitor or printer make
information you input available for you to view or use.
Monitors:
A monitor's front is called a screen with a cathode ray tube (CRT)
attached to the screen. Portable computers use a (LCD) liquid
crystal display. Today's super video graphics array (SVGA)
monitors display 256 sharp and clear colors.
Printers
A device that prints text or illustrations on paper. There are
two different types of printers.
1) Impact printer
2) Non Impact printer
Impact printers
Include all printers that work by striking an ink
ribbon. Dot-matrix are impact printers.
Dot-matrix:
Creates characters by striking pins against an ink
ribbon. Each pin makes a dot, and combinations of dots
form characters and illustrations.
Non-impact printers
Include laser printers and ink-jet printers. The important
difference between impact and non-impact printers is that impact
printers are much noisier.
Ink-jet:
Sprays ink at a sheet of paper. Ink-jet printers produce high-quality
text and graphics.
Laser:
Uses the same technology as copy machines. Laser printers produce
very high quality text and graphics.
Thermal printer:
Uses heat on chemically treated paper to form
characters
An inexpensive printer that works by pushing
heated pins against heat-sensitive paper.
Thermal printers are widely used in calculators
and fax machines.
A device that draws pictures on paper
based on commands from a computer.
Plotters differ from printers in that they
draw lines using a pen. As a result, they
can produce continuous lines, whereas
printers can only simulate lines by printing a
closely spaced series of dots.
Plotters are considerably more expensive
than printers. They are used in engineering
applications where precision is mandatory.
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Audio Output Devices
◦ Windows machines need special audio card for
audio output.
◦ Macintosh has audio playback built in.
◦ Audio output is useful for:
 Music
 CD player is a computer.
 Most personal computers have CD players that can access
both music CDs and CD-ROMs.
 Multimedia
Integrated Drive Electronics (IDE) Controller
This is the primary interface for the hard drive, CDROM and floppy disk drive.
Peripheral Component Interconnect (PCI) Bus
The most common way to connect additional
components to the computer, PCI uses a series of
slots on the motherboard that PCI cards plug into.
SCSI
Pronounced "scuzzy," the small computer system
interface is a method of adding additional devices, such
as hard drives or scanners, to the computer.
AGP
Accelerated Graphics Port is a very high-speed
connection used by the graphics card to interface
with the computer.
Sound card
This is used by the computer to record and play audio
by converting analog sound into digital information
and back again.
Graphics card –
This translates image data from the computer into a
format that can be displayed by the monitor.
Parallel Port
USB Ports
Serial Ports
SERIAL PORT
• Considered to be one of the most basic external
connections to a computer, the serial port has been
an integral part of most computers for more than 20
years.
• Although many of the newer systems have done
away with the serial port completely in favor of USB
connections, most modems still use the serial port, as
do some printers, PDAs and digital cameras. Few
computers have more than two serial ports.
Parallel Ports
If you have a printer connected to your computer, there is
a good chance that it uses the parallel port. While USB is
becoming increasingly popular, the parallel port is still a
commonly used interface for printers. Parallel ports can be
used to connect a host of popular computer peripherals:
• Printers
• Scanners
• CD burners
• External hard drives
• Iomega Zip removable drives
• Network adapters
• Tape backup drives
Universal Serial Bus (USB) Ports
The goal of USB is to end all of these headaches. The Universal
Serial Bus gives you a single, standardized, easy-to-use way to
connect up to 127 devices to a computer.
Just about every peripheral made now comes in a USB version. A
sample list of USB devices that you can buy today includes:
Printers
Scanners
Mice Joysticks
Flight yokes
Digital cameras Webcams Scientific data acquisition devices
Modems
Speakers
Telephones
Storage devices such as Zip drives
Video phones
Network connections
Connecting a USB device to a computer is simple -- you find the
USB connector on the back of your machine and plug the USB
connector into it.
The rectangular socket is a typical USB socket
on the back of a PC.
A typical "B" connection
A typical USB connector,
called an "A" connection
Power supply
An electrical transformer regulates the electricity used by
the computer.
Hard disk
This is large-capacity permanent storage used to hold
information such as programs and documents.
Operating system
This is the basic software that allows the user to interface
with the computer.
Secondary Memory
 Secondary storage is also know as auxiliary memory, this
memory is non-volatile.
 Secondary memory can store large volume of data on a
permanent basis
Secondary
Storage Devices
Direct Access Device
Sequential Access
Device
Magnetic
Tape
Magnetic Disks
Optical Disks
CD-ROM
Floppy
Disk
Hard
Disk
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The four most important characteristics of
storage devices:
◦ Speed and access time
◦ Capacity
◦ Type of access
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Speed (Access time) - How fast information
can be taken from or stored onto the
computer memory device’s medium.
◦ Electronic circuits: Fastest to access.
 40 billionths of a second.
◦ Floppy disks: Very slow in comparison.
 Takes up to 1/2 second to reach full speed before
access is even possible.
Capacity –
The amount of information that can be stored
on the medium.
Unit
1 bit
1 nibble
1 byte
1 kilobyte
1 megabyte
1 gigabyte
1 terabyte
Description
1 binary digit
4 bits
8 bits
1,024 bytes
1,048,576 bytes
1 million bytes
1,073,741,824 bytes
1 billion bytes
1 trillion bytes
Approximate Size
1 character
1/2 page, double spaced
500,000 pages
5 million pages
5 billion pages
There are two methods of accessing information1. Sequential access
2. Direct access
Sequential Access:
• Information on a sequential access device can only be retrieved in
the same sequence in which it is stored. For example: preparation of
monthly pay slips, monthly electricity bills etc.
• Magnetic tape is an example of a sequential-access storage device.
• The magnetic tape is a plastic ribbon, ½ -1/4 inch wide and 50-2400
feet long. The tape ribbon is itself stored in small cartridge or
cassette.
Direct Access:
• Information on a direct access device can be retrieved randomly.
• Magnetic disk is the storage medium for direct access
• Magnetic disk is broadly classified into 2 types:
• Floppy Disk
• Hard Disk
Floppy Disk:
A floppy disk is a circular piece of oxide-coated plastic that stores
data as magnetic spots. Personal computers most commonly use floppy
disks that are 3 ½ inches in diameter.
A Floppy disk drive is used to read/write data from /to floppy disks.
Hard Disk
Hard Disk is the secondary storage device, which are made
of rigid metal.
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Optical Disks: CD-ROM and DVD
◦ CD-ROM (Compact Disk - Read Only Memory)
 By its definition, CD-ROM is Read Only.
 Special CD drives “burn” information into blank CDs.
 Burn: A laser is used to “burn” craters into the surface to
represent a binary 1.
 Two main types of CDs:
 CD-R (Compact Disk - Recordable)
 CD-WR (Compact Disk - ReWritable)
 It takes longer to write to a CD-R than a hard drive.
 Special software is needed to record.
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DVD (Digital Versatile Disk)
◦ Allows up to 17 gigabytes of storage (from 4.7 GB
to 17 GB).
◦ Compatible with older CD-ROM technology.
Hand-held Computer
A hand-held computer or personal organizer is a small
portable computer with various functions, for example diary,
phone book, note book, etc.
Personal Computer
PC or desktop computers are used both in isolation, for
example in home computing, and as networked computers (a
network is two computers or more that are linked together
either by cabling or infra-red).
Palmtop
More commonly known as Personal Digital Assistants
(PDAs), palmtops are tightly integrated computers that
often use flash memory instead of a hard drive for
storage.
These computers usually do not have keyboards but
rely on touchscreen technology for user input
Workstation
A desktop computer that has a more powerful
processor, additional memory and enhanced capabilities
for performing a special group of task, such as 3D
Graphics or game development.
Laptop computer
Laptop
computers have similar computing power to
personal
computers, but are much lighter and
portable.
Laptops have a removable, chargeable battery pack so
that
the user does not always require a mains
electricity supply for its` use.
Server
A server is a large powerful computer, usually with a large
amount of storage (hard drive) space. Networked
computers are attached to one or more central network
servers, allowing users to share files, use network
software (e.g. a large email client), or connect to the
internet.
A Server may act as one or more of:
- compute server: to run programs
- file server: to store files centrally
- mail server: to route mail messages
- web server: to store web files etc.
Main Frame
The main frame is the workhorse of the business world.
A main frame is the heart of a network of computers or
terminals which allows hundreds of people to work at the
same time on the same data.
Supercomputer
The supercomputer usually costs hundreds of thousands
or even millions of dollars
These are used for jobs that take massive amounts of
calculating, like weather forecasting, engineering design
and testing, serious decryption, economic forecasting, etc.
Minicomputer
Minicomputers fall in between microcomputers (PCs) and mainframes
(enterprise servers).
In fact, the ordinary new PC is much more powerful than
minicomputers used to be.
Originally this size was developed to handle specific tasks, like
engineering and CAD calculations.
Hardware and Software
Hardware is any physical part of the computer setup. This
means the monitor, keyboard, mouse, CD-ROM drive,
printer, etc.
Software consists of the programmes that allow you to
work on a computer. Operating systems, word processors,
spreadsheets, games and database management systems
are all examples of software.
Hand-held (HPC)
PDA
Desktop
Tower
Tablet
PC
Laptop/Notebo
ok
Workstation
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Why is it so important?
◦ The economies of ALL developed nations are
dependent on software.
◦ More and more of our daily lives are being
supported/monitored by software
 The engines of our cars
 Our washing machines
 Getting on a bus/train
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Software is the part of a
computer that makes it useful.
Software is a set of instructions
Software
(Programs).
◦ These are acted upon (executed) by
the hardware.
◦ Software is also the documents that
describe the operation and use of
the programs.
The Computer
{
Application
Operating System
• Windows 98/2000/XP
• Linux/Unix
• Browser
• Email
• Word Processor
Hardware
Application
Operating System
Hardware
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Generally software takes in data and
processes it into information.
From the
user/device
/sub-system
Data In
Processing
Information
Out
To the
user/device
/sub-system
Application
Operating System
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System Software
Hardware
◦ This type of software exists at the Operating
System layer. It is the operating system itself,
compilers, editors….any kind of software that
supports the execution and/or development of
applications.
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Application Software
◦ Real-time Software
 Programs that monitor/analyse/control real world
events. A nuclear power plant cooling system is a
good example.
Application
Operating System
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Application Software
Hardware
◦ Business Software
 Business Information Systems such as payroll,
accounts and order management/tracking. There are
off-the-shelf packages available for small businesses,
however large businesses usually develop their own
software.
◦ Engineering and Scientific Software
 Typically ‘number crunching’ programs for areas such
as astronomy, molecular biology, weather forecasting
and Computer Aided Design (CAD) for engineers.
Generic programs do exist for some of these areas,
however research usually requires new software to be
developed.
Application
Operating System
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Application Software
Hardware
◦ Embedded Software
 Intelligent products such as cookers, washing
machines and microwaves use embedded software that
typically resides in a Read Only Memory (ROM). Due to
the individual nature of such products this software is
usually developed/tailored for each.
◦ Personal Computer Software
 Spreadsheets, word processors, computer graphics,
multimedia and database applications are typical. This
type of software is predominantly off the shelf but
does go through many versions to remove bugs and
increase functionality.
Application
Operating System
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Application Software
Hardware
◦ Artificial Intelligence (AI) Software
 AI is used to solve complex problems such as
scheduling the maintenance of manufacturing
equipment to minimise their shutdown. Other uses
include pattern recognition (speech/visual). This
software is typically newly developed for each
application.
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The application of computers through
software development is only limited by our
imaginations……(and its’ cost)
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As hardware will always eventually wear out,
it will need to replaced.
Software on the other hand, doesn’t wear
out in this traditional sense, but will
become increasingly less useful as users
requirements for it changes over time.
◦ This means that software needs to be either
periodically updated or replaced.
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Understanding the process of software
development is therefore paramount in
keeping software systems/applications
continually useful to its users.