Introduction, and Definition of a Computer
There are many electronic devices that can be classified as containing
a computer. An alarm clock, a calculator, and a television set are all examples of devices
that contain computers.
The simplest definition to suit our needs here, is the definition of
the desktop computers which we all use in our jobs.
A Computer is used to Store, Manipulate, and Retrieve information. A
Computer can be programmed to store, manipulate, and retrieve information in any format
that a programmer or user desires.
Think of your desktop computer as file cabinet with two drawers in it.
Think of the top drawer as containing all of the data you have stored
in your cabinet and the bottom drawer containing all of the policies and procedures you
follow when storing and retrieving data from the top drawer.
The Operating System, or OS
In the above example (Analogy 1), you can think of the
appearance of the file cabinets as the Operating Systems (OS) or Interface to your data
and to the policies and procedures. In the above example, there are three completely
different colors, shapes, and sizes of file cabinets. However, they can all contain
basically the same data and policies and procedures. This is very much like the
differences between using the Macintosh, Windows 95, Windows NT, Unix, and VMS Operating
Systems. The biggest differences are only in appearance, and the number of drawers they
contain. They also differ in the types of Policies and Procedures which programmers have
written for them.
File Systems and Applications
As in the file cabinet example (Analogy 1), computers store
information in Drawers, Folders, and Files. Drawers can be visualized as the Hard Disk
Drives of your computer. Most computers only have one hard drive, which would mean
that in Analogy 1, you would have both your data, and your policies and procedures
in the same drawer. You would simply divide them into different areas using folders
All computers systems, regardless of the Operating System (OS), use
folders, also referred to as Directories by some OSes, to store files and
information in. They simply present the folders to you in a different format or
All computer systems, regardless of the Operating System (OS), use Applications
or Programs to manipulate, retrieve, and display information back to computer
users. In Analogy 1 the Policies and Procedures would be the Applications/Programs.
On a Microsoft Windows desktop computer, the Policies and Procedures, or Applications, are
typically located in the "Program Files" folder of the computers C drive
(drawer). However, users can put these programs anywhere on their computer that they
prefer, at the time of installation.
Examples of Applications or Programs are the popular Microsoft products
like Word, Excel, Outlook, and Exchange.
The Binary Language of ALL computers
Just as humans have language, so do computers. The basic language of
computers is far more simplistic than that of humans though. The alphabet of the basic
computer language (Binary meaning TWO) consists of TWO numbers only. ZERO & ONE (0,1).
These binary characters are referred to as BITS of data.
This may prompt you to ask, "Then how does a computer have
information stored in human languages like English and French?". Just like the human
language uses a sentence to convey a message, computers must string these BITS into a
sequence (like a sentence) in order to describe something more meaningful to us humans
like an English character. BITS are strung together in sequences of 8. 8 BITS is
called a BYTE of data. The BYTE sequence 01000001is equal to the uppercase letter
A. The BYTE sequence is translated to an A by the Operating System and Applications
running on your computer.
8 Bits = 1 Byte
1024 Bytes = 1 KiloByte (KB)
1024 KiloBytes = 1 MegaByte (MB)
1024 MegaBytes = 1 GigaByte (GB)
1024 GigaBytes = 1 TeraByte (TB)
How Information is Stored
The hard drive of your computer is basically a bunch of tiny magnets.
When you save something, such as a Microsoft Word document, your computer magnetically
charges some of these tiny magnets, and leaves some of them without a charge, creating a
sequence of Bytes describing your document and it's contents. Charged magnets are
interpreted as one's, and the uncharged magnets are interpreted as zero's.
The distinction between hardware and software
As discussed above, computers store and use
information as Ones and Zeros, or magnetically charged bits of data. This
information can and does change often and therefore has earned the title of software. Your
computer however is comprised of hardware which does not change. Although the software
loaded onto the hard drive of your computer changes, the actual composition of the hard
drive does NOT change. Your hard drive is an example of your computer hardware.
Inside the Body and Mind
In the following analogy, it is important to understand that analogy 1
is best suited to describe the SOFTWARE of your computer. The following is better
suited to describe the HARDWARE of your computer. Hardware and Software go hand in
hand, but I will use different analogies to describe them as I hope it will help you to
better understand them.
Perhaps the best analogy to describe your
computers hardware is to think of your computer as a human body.
One of the main purposes of computers today is to do the
work of humans, yet at a much faster rate. It makes sense that computers are similar to
humans in design.
The Motherboard [Torso]
Just as the human TORSO serves as a central point
connecting us to our arms, legs, and head, a computers Motherboard serves a
computer by connecting all its parts to a central location. If you were to take apart your
computer, you would see a motherboard similar to the one below.
The Central Processing Unit (CPU) [Brain]
In humans, the brain serves as the focal point for all things that a
human does. The brain sends signals through the body to command it to do things. The brain
in turn receives messages from the body telling it how to feel. Like HOT when you spill
coffee on yourself. The Pentium PRO CPU is simply a square looking chip that plugs into
your motherboard. Pentium II and other CPUs look far different that this one.
Random Access Memory (RAM) [Short-Term Memory]
The primary function of your CPU is to process information. If an
application or software product, which you installed on your computer, needs to
temporarily store some information while it is processing something else, it can make use
of your computers RAM, or short term memory. RAM is almost identical to the hard drive in
your computer in theory. However, the difference is that RAM can be written to, and
accessed far faster than the hard drive. Also, once your computer has been turned off, it
loses all of its short-term memory, and must rely on its long-term memory, or the hard
drive when the computer is turned back on.
The above picture is an example of TWO memory SIMMs (single
in-line memory module) inserted onto a motherboard.
Hard Drive [Long-Term Memory]
As mentioned previously, the hard drive of your computer is where
information is stored in your computer. Sometimes when you are running a program on your
computer, you may hear a fast clicking sound while it is working. This may be your hard
drive spinning. Sometimes, if you do not have an adequate amount of RAM [short-term
memory] in your computer, programs will make use of your hard drive [long-term memory] to
temporarily store information while processing is taking place. This is often a culprit of
poor performance and may justify increasing the amount of RAM that your computer has.
Floppy Drives & CD ROMs [Other forms of Long-Term
Before networks and the Internet, there was still
a need to exchange information between people and computers. This was accomplished with
the Floppy diskette.
The standard floppy 3 ½" floppy disk can
hold up to 1.4 MegaBytes (MB) of information and can be used to exchange small to medium
sized documents between computer users.
When companies want to sell you their Software and Applications, they
may have a need to provide you with FAR more information than can be stored on 1.4 MB of
storage. For this, the Compact Disk [CD-ROM] can be used.
The standard Compact Disk can hold up to 650MB of
data. Sufficient for even the most robust applications. The primary difference between a
CD and your computers hard drive is that the CD doesnt use tiny magnets to
store the information on. The CD uses pits or dips in its surface. If a pit is depressed,
then the value is a One, if the pit is not depressed, then the value is Zero. The pits are
read using a laser beam in your CD-ROM Drive.
Technology has grown more advanced in recent years with the development
of the DVD Disk [Digital Versatile Disk]. The DVD is the SAME exact hardware as a Compact
Disk. The only difference is in the size the pits. The DVD uses a combination of smaller
pits, both sides of the disk, and in some cases translucent layering to increase the
number of pits that can be stored on the disk. Currently, DVD can support up to about 17
Gigabytes (GB) of data. This amount is sufficient to store a feature length film on.
ISA and PCI expansion slots [The Arms and Legs]
We have discussed some of the primary components
of a computer and shown the analogy they have to the human body. The next part of this
analogy is that of the Arms and Legs of the computer. Just as we humans use our arms,
hands, and legs to interact with the environment around us, computers have ISA (Industry
Standard Architecture) and PCI (Peripheral Component Interconnect) slots. These slots
allow us to install additional components in our computers making it possible for them to
interact with other systems or environments around them.
Some examples of devices which can take advantage of these expansion
||By installing a modem in an available PCI or ISA slot,
your computer can communicate with other computer systems or fax machines by making a
connection over a standard phone line. If youve dialed into the Internet, or AOL, or
CompuServe, it is possible that youve seen the message "Shaking Hands" or
some message similar to this. Just as humans can shake hands, computers can use their
modems to do the same over a phone line. This is a way of initiating communication between
the two systems.
||Identical in theory to a modem, is a network card. The
only difference between a network card and modem is that a modem is used primarily over a
phone line. A network card uses a different type of connection that allows us to connect
computers together with a much faster connection. Phone Lines do not currently support the
same high speeds that can be attained inside a company using network cards.
||Small Computer System Interconnect. This type of card
allows you to install up to 6 different devices using only ONE available slot. Hard
drives, CD-ROMs, scanners, and ZIP drives are just a few examples of the types of
devices that you can connect to a SCSI card.
The Monitor, Keyboard, and Mouse [Mouth, Ears, and
In order for use humans to know what is going on
inside the computer, it makes use of the Monitor to display information to us [The
In order for us to communicate to the computer
what it is we want it to do, we type information into the keyboard, and point and click on
things with the mouse [The computers ears and eyes].
Do not confuse dumb terminals with a Computer like a PC or Macintosh. A
dumb terminal earns the name dumb because it has no CPU [Brain], RAM [Memory], or Hard
Drive [Long Term Memory]. A dumb terminal has only one purpose. To serve as an interface
to a remote mainframe computer typically located somewhere else in your company. The
biggest indicator that you are using a dumb terminal is if there is no mouse. Dumb
terminals do not use a GUI (Graphical User Interface). They typically use character-based
menus with no pictures at all. They also typically only display two colors, black being
the background color.
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Last Modified on Tuesday, May 11, 1999