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Computer Hardware and Software Concepts Handout (PDF)

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					                                    CPCA 105
                        Introduction to Personal Computers




Computer Hardware and Software Concepts Handout


A basic computer system is defined as a device that accepts input, processes data, stores data,
and produces output. A personal computer system includes a computer, peripheral devices, and
software. Microcomputers can range in size from hand-held models like the PalmPilot to laptop
or notebooks to desktop models.

The following diagram illustrates the fundamental computer functions and components that help
the computer accomplish its tasks.




Figure 1: Basic computer functions




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Computer Hardware


    Computer hardware refers to the physical components of a computer system. Hardware
    appears both inside and outside the computer. Peripheral devices are equipment used
    with a computer to enhance its functionality. They are devices that are “outside” of or in
    addition to, the computer (i.e. printer, scanner, and modem). The following diagram
    displays the hardware devices found on most personal computer systems.




    Figure 2: Hardware Devices




    System Unit, Central Processing Unit, and Random Access Memory

    The system unit is the cabinet that contains many of the computer’s working
    components. One of the most important of these components is the central processing
    unit (normally referred to as the CPU). The CPU, a small electronic circuit chip, is the
    heart of the computer system and is the device that allows the machine to perform its
    complex mathematical and logic functions. The CPU is considered the “brains” of the
    computer system. Although it is not important to know how the CPU works in order to
    be able to use the personal computer, it is important to know that it is a major part of the
    machine.




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           The CPU chip is identified by a name and/or number that indicate its computing
           capabilities. For example, a basic PC might have a Celeron chip, whereas a more
           powerful system might have a Pentium III or Pentium 4 chip. Higher-numbered CPU
           chips will perform tasks faster and allow the computer to do more things.

           CPU chips are also rated in terms of processor speed, which is measured in megahertz
           (MHz) or gigahertz (GHz). When comparing two Pentium chips, the higher processing
           speed will normally indicate the more powerful computer. Typical processor speeds
           range from 500 MHz to 3 GHz. It is important to remember when evaluating a computer
           that the chip type (Celeron, Pentium III, or Pentium 4) will determine the overall
           computer performance to a greater degree than the processing speed.
RAM Chip

           As you work on the computer, the programs used to run the computer and the information
           you enter is stored in a temporary area of the computer’s memory referred to as RAM or
           random access memory.

           Ram is stored on electronic chips connected to the main board in the system unit (the
           motherboard) next to the CPU. The amount of RAM in a computer depends on the size
           and number of RAM chips the computer contains. As RAM increases, more information
           and programs can be used at one time.

           RAM is measured in bytes; you can think of each byte as being equivalent to one
           character. RAM chips are measured in megabytes (meg means a million; abbreviated
           MB). Less-powerful computers come with 128 MB RAM; newer, more powerful
           computers come with 512MB, 1GB or more RAM. Many newer programs operate more
           efficiently with increasing amounts of RAM. Windows XP requires a minimum of 64
           MB and computers with 128 MB or more of memory is preferred. Fortunately, it is easy
           to add additional memory to most personal computers.

           The most important thing to remember about RAM is that it is volatile; that is, whatever
           is in RAM exists only while the computer is on. As soon as you turn off the computer or
           exit the program with which you are working, the information is lost. In addition, if the
           computer is accidentally shut off – such as with a power failure, lightening storm, or the
           plug coming out – everything is lost. There is, however, a way to save your program and
           information by storing it on disks.


           Storage Devices and Storage Medium

           Since RAM is volatile and everything is lost when you turn off your computer, you need
           a way to store the information you enter and the documents you create. A fairly
           permanent way to store information is to use one or more storage devices, found both
           internally and externally on most personal computer systems. Examples of storage
           devices include hard disk drives, floppy disk drives, CD-writers, DVD drives, Zip®
           drives, and flash drives. Each storage device (except for the hard drive) also requires a
           storage medium that actually holds the data. These storage medium devices include
           floppy disks, CDs, DVDs, Zip® disks, flash drive, and tapes. (We say the storage is

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“fairly permanent” since unforeseen things can happen, even to a storage medium such as
a floppy disk or Zip disk.)

The main storage device on a personal computer system is the internal hard drive. It
holds both data and program files. Hard drives come in different sizes, measured in
megabytes or gigabytes (billions of bytes). Sample sizes of hard drives include 40GB,
80GB, 100GB. The hard drive is generally referred to as drive C:.

Floppy disk drives can hold 3.5” floppy disks. The floppy drive is generally referred to
as drive A:. Since most new computers have omitted the floppy drive as a storage
medium option, those computers do not contain an A: drive. High-capacity Zip drives
holds 750 MB of data. The letter identifier for the ZIP drives, CD drives, DVD drives,
and flash drive depend on how the computer is configured. It may vary from computer to
computer.

A CD (compact disk) provides 650-700 MB of storage. A DVD (digital video disk or
digital versatile disk) has a capacity of 4.7 GB. CDs and DVDs are durable storage and
have a higher tolerance for temperature fluctuations then hard disk, floppy disks, and
tapes. They are unaffected by magnetic fields and dust and dirt can be cleaned off easily.
The biggest threat is scratches.

CDs and DVDs come in several varieties:
  • Read only (ROM) – permanent data stored during manufacturing
  • Recordable (R) – A writable drive can store data but it can’t be changed
  • Rewritable (RW) – can be changed many times, much like a hard drive but much
      slower

A USB flash drive is a popular portable storage device. It is about the size of a
highlighter pen and is very durable. It plugs into a USB port at the back of the computer
and provides fast access to data. The advantages of the USB flash drive are:
   • It is very durable
   • You can open, edit, delete, and run files just as if they were on hard drive
   • It plugs into USB port
   • Provides fast access to data and uses little power


In addition to storage devices connected to the computer, data can be stored on remote
devices such as network hard drives and virtual drives on the Internet. The advantages of
remote storage devices include:
    • More storage then personal computer
    • Easily accessible to others for collaborative work
    • Potentially safe storage if computer is damaged or stolen




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Basic Input Devices

Keyboard

The keyboard is the standard device used to enter information into the computer’s
memory. It looks and operates much like a standard typewriter keyboard and includes
the 26 letters of the alphabet, the 10 digits used for numbers, and some special characters.
In addition to these standard keys, the keyboard also has special sets of keys.

On the right-hand side of the keyboard is the numeric keypad. To the left of the
numeric keypad are the arrow keys, Home, End, Pg Up, and Pg Down keys, which allow
movement around the computer screen. At the top or left-hand side of the keyboard are
keys labeled F1, F2, F3,…F12. They are referred to as function keys. These keys
perform special functions depending on the program you are working in.

Other special keys you will use include:


Shift:               The Shift key works like the familiar shift key on a typewriter.

Alt:                 The Alternate (Alt) key is used in combination with other keys to
                     send special commands to computer programs.

Ctrl:                The Control (Crtl) key works like the Alt key. It is always used in
                     combination with some other key.

Esc:                 The Escape (Esc) key is used to escape or leave some function you
                     have selected. The Escape key is always used by itself.

Enter:               The Enter key is typically used to end a paragraph when working in
                     most application programs or to execute a command.

Tab:                 The Tab key is typically used to move the insertion point across the
                     screen to the next tab stop, in the same manner as a tab key on a
                     typewriter.

Backspace:           The Backspace key, located directly above the Enter key, deletes the
                     character to the left of the insertion point.

Delete:              The Delete key, located to the right of the Enter key, deletes the
                     character to the right of the insertion point.

All the keys on the keyboard are auto-repeat keys. This means that if you hold the key
down, the character or function that the key performs will be repeated as long as the key
is held down.



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The Mouse

A mouse is a special pointing device that helps you manipulate objects and select menu
and toolbar options. The bottom of the mouse contains a small ball that rolls when you
move the mouse. As the ball rolls, it causes a special signal to be sent to the computer,
moving the mouse pointer in the direction you are moving the mouse. The PC mouse
contains two buttons – with right mouse button used primarily for shortcuts.



Basic Output Devices

Video Monitor

The video monitor (also called the screen or display) serves as the standard output
device for the computer system. Most monitors are full-color monitors and are available
in different resolution levels, or clarity. A higher-resolution monitor will provide the
sharpest picture, but will be more expensive than a lower-resolution monitor. Most
monitors can display at least 256 colors. Monitors are also available in different sizes
such as 15”, 17”, or 20” screens. Flat-panel monitors which use LCD (liquid crystal
technology) are much thinner than CRT monitors and range in depth from one to four
inches. The more expensive flat-panel models can function as a computer monitor, a TV
and a video monitor - all in one.



Printers

A printer is used to produce a “hard” or printed copy of the information stored in the
computer system. Ink-jet printers produce characters by spraying ink onto the paper.
The print head is a matrix of fine spray nozzles. Color ink-jet printers have excellent
resolution and print at a respectable rate. Ink-jet printers provide low-cost, high-quality
print on plain paper.

A laser printer provides superb quality print and is capable of printing most any graphic.
They are more expensive than dot matrix printers, but their quiet, high-quality print
provides the best output possible, especially when you are printing charts or other types
of graphics. Laser printers can print an entire page at a time and are usually faster than
dot matrix printers. These are the printers you would like to use when you want the best
print quality possible.




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    Computer Networks

    A computer network consists of two or more computers connected in some way so that
    they can share hardware (printers, storage devices), software programs, data, and other
    resources. Each microcomputer connected to a network is referred to as a workstation
    (or client). Data is sent from one device on a network to another over a cable or by a
    wireless signal.

    The network server (or host server) is a network resource. It distributes application
    programs and data files to the workstations. The hard disk drive of the network server is
    shared by the workstations on the network. A network printer is a network resource
    because any connected workstation can send files to it.

    Even though a computer workstation is connected to a network, it still contains the same
    local resources as a computer that’s not connected to a network. The workstation’s
    memory, processor, and storage devices are available locally, as are the programs and
    data files stored on the hard drive.

    A network that is located within a relatively limited area, such as a building or campus, is
    referred to as a local area network (LAN). LANs are found in many homes, businesses,
    government offices, and educational institutions.

    A network that covers a large geographical area is referred to as a wide area network
    (WAN). WANs can connect hardware resources across campus, across town, or across
    the country. The Internet is the largest known WAN. It connects millions of LANs and
    WANs around the world.




Computer Software Concepts
    The term software refers to the programs or instructions that enable the computer to
    perform its tasks. There are basically two types of software programs that the computer
    uses of which you need to be aware: the operating system programs and the application
    system programs.

    Operating System

    An operating system controls the resources and components of the computer. It consists
    of many specialized programs, each of which performs a special task. One task
    controlled by the operating system is the allocation of the computer’s RAM to application
    programs. The operating system is also responsible for the synchronization of hardware
    components such as the monitor, printer, and disk drives.




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     Applications Software

     Application software refers to the programs written to perform useful functions. The
     most popular application programs are described below:

     •   Word processing software, such as Microsoft Word, is used for producing reports,
         letters, papers, and manuscripts.
     •   Desktop publishing software, such as Adobe In-Design, helps you use graphic design
         techniques to enhance the format and appearance of documents such as newsletters,
         brochures, newspapers, and magazines.
     •   Web authoring software, such as Microsoft FrontPage or Macromedia Dreamweaver,
         helps you design and develop customized Web pages.
     •   Spreadsheet software, such as Microsoft Excel, helps you create worksheets to
         perform calculations, create “what-if” analyses, and graph data.
     •   Database software, such as Microsoft Access, helps you keep track of related data
         and records. Other functions include finding, organizing, updating, and reporting
         information stored in more than one file.
     •   Presentation software, such as Microsoft PowerPoint, helps you to combine text,
         graphics, animation, and sound into a series of electronic slides.
     •   E-mail software, such as Microsoft Outlook, helps you to send and receive e-mail
         messages over the Internet.




Disk and File Concepts

     When you store information on a disk, you store it as a file. A file is a collection of
     information saved under one name.

     Since we will be using floppy disks as the main storage medium for our data files, a brief
     explanation of floppy disks appears below.

     Floppy Disks
     The density of the floppy disk determines how much information it can store; the higher
     the number, the more information. A low-density (double density) floppy disk stores 720
     KB of data; the high-density disk stores 1.44 MB.
     In addition to size and density, disks differ in whether they store information on one or
     both sides. Early computers used disks that stored information on a single side and in a
     single density format, called SS/SD. Today’s computers use disks that store
     information on both sides in a double-sided high density (DS/HD) format.




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Formatting Floppy Disks

When something is written to a disk, the information is recorded magnetically in
concentric circles called tracks. These tracks are then further subdivided into sectors.
The computer’s operating system and disk drives know where information is stored by
maintaining the track and sector numbers.
 Tracks and sectors are not on new unformatted disks and must be created by the
computer before you can store information on the disks. The process of creating tracks
and sectors is called formatting or initializing. (Note that most disks come pre-
formatted.) You can format a new disk or a disk that has been previously formatted and
has information on it. An important point to remember is that when you format a disk, it
destroys all of the information on the disk.

Naming Files

Disks, especially hard disks, can contain many (sometimes several hundred) files.
Therefore, to be able to find a file and access its information, each file must have a
different name from any other on the same disk therefore, the filename must be unique.
The file name is assigned by the user and can contain spaces and some special characters.


Loading and Saving Files

To use a file on disk, you must load the file into memory. This process creates a second
copy of the file in random access memory (RAM). The copy that is on the disk remains
there and is not changed until you save your work.

When you make changes to the copy of the file on the screen, only the copy of the file in
RAM, not the copy of the file on the disk, is altered. No changes are made to the copy of
the file on the disk until you instruct the computer to save it to the disk.


Folders
After you have been working with a computer for a while, you will probably have many
files. The computer provides a way for you to organize your files so you can retrieve
them quickly and easily. You can create folders using Windows XP that let you organize
files that are related under some topic or area. Each folder can contain documents,
programs, graphics, or other related material. Think of these computer folders as an
electronic manila cardboard folder in which you can save your electronic files.

For example, suppose you want to organize your computer work according to subject
matter, namely, Word Processing, Spreadsheet, and Database. You would create folders
on your disk for each subject matter and move the files into the appropriate folders so that
you could quickly find the information you were looking for.


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Recommended computer maintenance and care
   • Environmental factors can do damage
        – Excess heat can damage circuitry
        – Excess humidity combined with salt air can corrode contacts
        – Magnetic fields can erase data
        – Dust and dirt can cause overheating and clog up mechanical parts

   •   Routine cleaning of mouse and keyboard can keep them working smoothly
   •   Follow manufacturer’s instructions for cleaning to keep printer from jamming and
       printer head from smearing
   •   Keep floppy disks and hard drives away from strong magnetic fields


   •   Computers are vulnerable to power irregularities
         – Make sure power cable is positioned so it can’t be accidentally disconnected
         – When going to another country, ensure your equipment conforms to power
            systems
         – Use surge strips to protect against power spikes and surges
         – To protect against power outages, you can connect to uninterruptible power
            supply

   •   As computer files are added/deleted, parts of files tend to become scattered all over the
       disk
   •   These fragmented files are stored in noncontiguous clusters
           – Slows drive performance
   •   Defragmentation utility – rearranges the files on a disk so that they are stored in
       contiguous clusters



   •   Owners should periodically make backups of data, run a defragmentation utility, and
       update virus checking software
   •   Consider following guidelines when troubleshooting:
          – Make sure equipment is plugged in
          – Check all cables
          – Get clear idea of problem by trying to isolate malfunctioning device or replicating
              steps


Rules for naming files:




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Computer virus

   •   A computer virus is a program that attaches itself to a file, reproduces itself, and spreads
       to other files
   •   A virus can perform a trigger event:
           – Corrupt and/or destroy data
           – Display an irritating message
   •   Key characteristic is their ability to “lurk” in a computer for days or months quietly
       replicating themselves

   •   Viruses are spread through e-mails as well
   •   Macro viruses are usually found in MS Word and MS Excel files (.doc and .xls)
   •   To keep safe, you can disable macros on files you do not trust

Symptoms of a virus




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Antivirus software is a set of utility programs that looks for and eradicates viruses

When should I use antivirus software:
  • “All the time”
  • Most antivirus software allows you to specify what to check and when to check it
  • Norton Antivirus
  • McAfee Antivirus




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