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Revision IT111 Computers Computing Revision 1 Elements of a Computer Communication

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Revision IT111 Computers Computing Revision 1 Elements of a Computer Communication Powered By Docstoc
					      IT111
Computers & Computing

      Revision

                        1
Elements of a Computer-
Communication System
1.   People
2.   Procedures
3.   Data/Information
4.   Hardware
5.   Software
6.   Communications


                          2
Elements of a Computer-Communication
System




                                       3
MODEM
• Modulator-Demodulator
• Converts (modulates) the digital signal into
  an analog signal, then transmits the signal
  over telephone lines.
• The receiving modem then converts
  (demodulates) the analog signal into a digital
  signal then releases the signal into the
  computer.
• Common speeds: 14.4, 28.8 & 56 kbps

                                                   4
Five Kinds of Computers
• Computers can be generally grouped into
  broad types based on their processing speeds
  and their capacity to store data.
•   Microcontrollers
•   Microcomputers
•   Minicomputers
•   Mainframes
•   Supercomputers


                                                 5
What is software?
• Software, or programs,
  consists of the instructions that
  tell the computer how to
  perform a task. There are two
  types of software,
  applications and system.

                                      6
Types of software
 Applications software has been
 developed to solve a particular problem,
 to perform useful work on specific
 tasks, or to provide entertainment.
 System       software      enables    the
 applications software to interact with
 the computer and helps the computer
 manage its internal resources.
                                             7
Types of software




                    8
Types of applications software




                                 9
Three Components of System
Software
• System software enables applications
  software to interact with the computer
  and helps the computer manage its
  internal and external resources.
• System software comprises three (3)
  basic components:
  – the operating system,
  – utility programs, and
  – language translators.

                                           10
Three Components of System
Software
 • Operating systems: An operating system is
   the principal piece of systems software in any
   computing system.
 • Utility programs: Utility programs are
   generally used to support, enhance, or expand
   existing programs in a computer system. Most
   system software bundles utility programs for
   performing common tasks such as merging two
   files into one file or performing backup. Other
   external, or commercial, utility programs (such
   as Norton Utilities) are available separately—for
   example, a utility to recover damaged files.
                                                   11
Three Components of System
Software
 • Language translators: A language
   translator is software that translates a
   program written by a programmer in a
   language such as C—for example, a word
   processing program—into machine
   language (0s and 1s), which the
   computer can understand.




                                          12
13
Machine Cycle




                14
Parity bit




             15
16
Softcopy VS Hardcopy
• Softcopy refers to data that is shown on
  a display screen or is in audio or voice
  form. This kind of output is not tangible;
  it cannot be touched.
• Hardcopy refers to printed output. The
 principal examples are printouts,
 whether text or graphics, from printers.
 Film, including microfilm and microfiche,
 is also considered hardcopy output.
                                               17
Printers: Impact vs Non-impact
• An impact printer forms characters or images by
  striking a mechanism such as a print hammer or
  wheel against an inked ribbon, leaving an image
  on paper. Impact printers are dying out. A dot-
  matrix printer contains a print head of small
  pins, which strike an inked ribbon against paper,
  forming characters or images. Color ribbons are
  available for limited use of color.

• Large computer installations use high-speed line
  printers, which print a whole line of characters at
  once rather than a single character at a time.


                                                   18
Printers: Impact vs Non-impact
• Non-impact printers are faster and
  quieter than impact printers because
  they have fewer moving parts.
• Non-impact printers form characters
  and images without making direct
  physical contact between printing
  mechanism and paper. Example:
  Laser printers, inkjet, thermal

                                     19
Non-Impact Printer: Laser
• A laser printer uses the principle of
  dot-matrix printers of creating
  images with dots.
• These images are created on a
  drum, treated with a magnetically
  charged ink-like toner (powder), and
  then transferred from drum to
  paper.
                                          20
Non-Impact Printer: Laser




                            21
Non-Impact Printer: Inkjet
• Ink-jet printers also form images with little
  dots. Ink-jet printers spray small, electrically
  charged droplets of ink from four nozzles
  through holes in a matrix at high speed onto
  paper.
• The advantages of ink-jet printers are that
  they can print in color, are quieter, and are
  much less expensive than color laser
  printers. The disadvantages are that they
  print in a somewhat lower resolution than
  laser printers and they are slower.
                                               22
Non-Impact Printer: Inkjet




                             23
Non-Impact Printer: Thermal
• For people who want the highest-quality
  color printing available with a desktop
  printer, thermal printers are the answer.
  Thermal printers use colored waxes and heat
  to produce images by burning dots onto
  special paper.
• However, thermal printers are expensive,
  and they require expensive paper. Thus,
  they are not generally used for jobs requiring
  a high volume of output.

                                            24
Computer Output Microfilm &
Microfiche
• Computer output microfilm is computer
  output produced as tiny images on rolls of
  microfilm; microfiche uses sheets instead
  of rolls. The images are up to 48 times
  smaller than those produced on a printer.
  Moreover, they can be recorded far faster
  and cheaper than the same thing on
  paper-printed output.


                                           25
Computer Output Microfilm &
Microfiche
• The principal disadvantage, however,
  is that a microfilm or microfiche
  reader is needed to read this type of
  output.
• It’s possible that this technology
  could be made obsolete by
  developments in secondary-storage
  techniques.
                                      26
Analog vs Digital




                    27
Communications Channel
 • Can be divided into two main categories:
   – Wired/guided media
      • Twisted pair wire
      • Coaxial cable
      • Fibre optic cable
   – Wireless/unguided media
      •   Microwave
      •   Satellite
      •   Global Positioning System
      •   Pagers
      •   Analog Cellular
                                          28
Twisted-Pair Wire
•      Twisted-pair wire consists of
    two or more strands of insulated
    copper wire, twisted around each
    other in pairs




                                       29
 Coaxial cable
• Coaxial cable, commonly called “co-ax,”
  consists of insulated copper wire wrapped in
  a solid or braided metal shield, then in an
  external cover.
• Coax is widely used for cable television. The
  extra insulation makes co-ax much better at
  resisting noise than twisted-pair wiring and
  it can carry voice and data at a faster rate.




                                              30
Fiber-optic cable




                    31
Microwave systems




                    32
Satellite systems




                    33
Advantages of Networks
• LANs, WANs, and MANs offer the
  following advantages:
 –   sharing of peripheral devices,
 –   Sharing of programs and data,
 –   better communications,
 –   security of information, and
 –   access to databases.


                                      34
Types of Networks
• Networks are categorized principally
  in the following three sizes:

• Wide area network (WAN)
• Metropolitan area network (MAN)
• Local area network (LAN)


                                         35
Topology of LANs
• The logical layout, or shape, of a network
  is called a topology. The five basic
  topologies are presented below:

  –   Star topology
  –   Ring topology
  –   Bus topology
  –   Hybrid/mesh topology
  –   FDDI topology

                                               36
   Serial & Parallel Transmission
• In serial data transmission, bits
  are transmitted sequentially, one
  after the other. Serial transmission
  is the way most data flows over a
  twisted-pair telephone line.




                                    37
    Serial & Parallel Transmission
• In parallel data transmission, bits
  are transmitted through separate
  lines simultaneously. Parallel lines
  move information faster than serial
  lines do, but they are only efficient
  for up to 15 feet.




                                          38
Direction of Transmission Flow
• Data can flow in three      ways
  between two computers:

 – Simplex transmission
 – Half-duplex transmission
 – Full-duplex transmission



                                     39
Simplex transmission
• In simplex transmission, data can
  travel in only one direction.




                                      40
Half-duplex transmission
• In half-duplex transmission data
  travels in both directions but only
  in one direction at a time.




                                        41
Full-duplex transmission
• In full-duplex transmission, data
  is transmitted back and forth at the
  same time.




                                         42
Transmission Mode
• Receiving equipment needs to know
  where one byte (or character) ends
  and another begins. This is
  resolved through either
  asynchronous transmission or
  synchronous transmission.



                                       43
Asynchronous transmission
• Asynchronous transmission: In
  asynchronous transmission (also called
  start-stop transmission) data is sent one
  byte (or character) at a time.
• Each string of bits making up the byte is
  bracketed, or marked off, with special
  control bits.
• Transmitting only one byte at a time
  makes this a relatively slow method,
  therefore this method is not used when
  great amounts of data must be sent
  rapidly.

                                         44
Asynchronous transmission




                            45
Synchronous transmission
 • Synchronous transmission sends data in
   blocks. Start and stop bit patterns, called
   synch bytes, are transmitted at the
   beginning and end of the blocks.
 • These start and end bit patterns
   synchronize internal clocks in the sending
   and receiving devices so that they are in
   time with each other.
 • This method is rarely used with
   microcomputers because it is more
   complicated and more expensive than
   asynchronous transmission.
                                           46
Synchronous transmission




                           47
Multiplexing
• Multiplexing is the transmission of
  multiple signals over a single
  communications channel.
• A multiplexer is a device that merges
  several low-speed transmissions into one
  high-speed transmission. High-speed
  multiplexers called T1 multiplexers,
  which use high-speed digital lines, can
  carry as many messages, both voice and
  data, as 24 analog telephone lines.

                                             48
Multiplexing




               49
Responsibilities of a DBA
• The DBA’s responsibilities include
  the following:
  – Database design, implementation,
    and operation
  – Coordination with users
  – System security
  – Backup and recovery
  – Performance monitoring

                                       50
Advantages of a DBMS
•   Reduced data redundancy
•   Improved data integrity
•   More program independence
•   Increased user productivity
•   Increased security



                                  51
52
53
Converting to a
new system:
four ways
Four strategies for converting
to a new system are direct,
parallel, phased,and pilot.




                                 54
ALL THE BEST
  IN YOUR
  EXAMS!!!
               55

				
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