In today's world, computers are used for almost
every task imaginable. Routine activities such as paying bills, buying
groceries, or communicating with a friend can be done with a computer. That is
why it is important not only to know how to use a computer, but also to
understand the components of a computer and what they do.
Recent studies report that almost 40% of homes
surveyed have personal computers, and this number is growing. Given the
widespread use of computers, computer literacy - a knowledge and understanding
of computers and computer uses - has become an essential ingredient in the
recipe for success in today's world. Florida
Collectively, the electric, electronic, and
mechanical equipment that makes up a personal computer is called hardware.
Devices that surround the system unit (i.e., the keyboard, mouse, speakers,
monitor, and so on) sometimes are known as peripheral devices.
Computers manipulate (process) data (input) to produce information
(output) and hold (store) that information for future use. These operations are
completed incredibly quickly. Today's supercomputer can perform 72 trillion
operations per second. If a person did one arithmetic operation a second without
stopping, it would take more than 31,000 years to perform the number of
operations a supercomputer can do in one second.
Data and
Information
A major part of understanding computers is to know
what goes into them (data), what comes out of them (information), and to
understand the process of turning data into information, also known as the
information processing cycle.
Understanding the difference between data and
information is important. Clifford Stoll - lecturer, computer security expert,
and author (The Cuckoo's Egg: Tracking a Spy through the Maze of Computer
Espionage and Silicon Snake Oil: Second Thoughts on the Information
Superhighway are two of his most popular works) - notes a wide gap between data
and information. Information has a pedigree, or lineage. Its source is known,
whether a respected professor or a seventh grader. "The Internet has great
gobs of data," Stoll maintains, "and little, little
information."
Components
of the Computer and Their Use
A computer consists of five primary hardware
components: input devices, the central processing unit (CPU), memory, output
devices, and storage devices. These components work together with software to
perform calculations, organize data, and communicate with other computers.
Different types of input devices transmit
different types of data or transmit data in different ways. A keyboard is used
to transmit alpha/numeric data by typing. In addition to the standard keys in
the typing area, an enhanced keyboard contains:
Function keys that can be programmed to perform specific tasks
Status lights that indicate modes that can be turned on and off
by toggle keys (e.g., caps lock and num lock)
A numeric keypad that allows for rapid entry of numbers
Arrow keys and other cursor-control keys (e.g., home, end,
page up, and page down) that control the on-screen movement of the insertion
point
Special keys such as esc, shift, ctrl, and alt that have
varying functions depending on the software
The mouse, like a trackball or joystick, is called a
pointing device because it controls the movement of a pointer, or mouse
pointer, on the computer screen. The first mouse was a one-button, rectangle
shaped device invented by Doug Engelbart in 1964. A mouse is very easy to use.
It requires empty desk space, however, and forces the user to remove a hand
from the keyboard to give a command.
Different CPUs function at different speeds. The rate at which
computer operations take place is measured in gig hertz (GHz), or billions of
electronic pulses per second. This rate varies among computers and should be a
consideration when purchasing a personal computer. Computers have two basic
types of memory. RAM (random access memory) is volatile, meaning that its
contents are lost when the computer is turned off. ROM (read-only memory) is non-volatile
because it retains its contents even when the power is turned off. ROM stores
information that does not change, such as the instructions and data used to
start the computer when it is first turned on.
Like input devices, different types of output
devices convey different types of information or convey information in
different ways. Printer output sometimes is called hard copy because of its
physical, touchable character. Monitor output, on the other hand, is called
soft copy because it has only an electronic, intangible existence.
Non-impact printers represent the fastest growing
segment of the printer market. The drops of ink that form an ink-jet printer
character are similar to the dots that form a dot matrix character figure, but there
are many more of them. Good quality paper must be used with ink-jet printers so
that the ink does not bleed. The speed quoted for impact printers often is
measured in characters per second (cps). Like ink-jet printers, laser printer
speed is measured in pages per minute (ppm). Although they are fast, all
printers are much slower than computers. Because of this, most printers have a
buffer that temporarily stores a few pages, allowing the computer to dump
output into the buffer and continue processing. The most widely used PC
monitors are 14- or 17-inch (measured from one corner to the diagonally
opposite corner). With the growing popularity of portable computers, the
clarity of LCD displays continues to improve. The quality of a monitor's
display depends largely on three factors:
·
Resolution - the number of pixels displayed
·
Dot pitch - the distance between pixels
·
Refresh rate - the speed with which images are redrawn on the
screen
·
Storage devices are different from memory. Memory,
sometimes called primary storage, is fast, short-term, volatile, and relatively
expensive. Storage devices, on the other hand, are slower, long-term, non-volatile,
and less expensive.
Floppy Disks
and Hard Disks
The data and information used in a computer needs
to be stored for future use. The memory of a computer only holds items
temporarily while they are being processed. When not being processed, these
items must be stored in auxiliary storage devices. These devices include floppy
disks, hard disks, CD-ROM, and DVD-ROM. When selecting a storage device it is
important to know that each device holds different amounts of information.
Although floppy disks once were available in two
sizes, the 5.25-inch floppy disk rarely is used today, and some believe it is
destined for the same fate as the eight-track tape. Because of its rigid
plastic shell, it may be difficult to see the 3.5-inch disk as
"floppy." The name is justified, however, not only by the disk's
ancestry but also by the flexible character of the disk itself. When a floppy
disk drive is reading from or writing to a floppy disk, a light turns on next
to the drive. Floppy disks never should be inserted into or removed from the
drive when this light is on. Most magnetic disks are read/write storage media.
Some optical discs, such as CD-ROMs, usually can be read from but not written
to. Each track on a formatted floppy disk is very narrow. To see how narrow,
try to draw 80 lines in a 11/4-inch space (the approximate radius of the floppy
disk surface). Floppy disks are soft-sectored, meaning that the number of
sectors is not predetermined. Floppy disk access time depends on the time
needed to locate the correct track, the time required to rotate the disk to the
proper sector, and the time necessary to transfer the data into main memory.
Although personal computer hard disks usually are
fixed (i.e., not removable), some portable computers have removable hard disk
drives. Unlike floppy disks, hard disks constantly are spinning, at a rate 10
to 20 times faster than floppy disks. Therefore, access time for hard disks is
significantly less than access time for floppy disks. While a floppy disk
read/write head rests on the disk, the read/write head for a hard disk hovers
about 10 millionths of an inch above the disk surface. Contamination on the
disk - a speck of dust (about 1550 millionths of an inch), a fingerprint (about
600 millionths of an inch), or a particle of smoke (about 250 millionths of an
inch) - can cause a "head crash," destroying data and rendering the
disk drive unusable. For this reason, hard disk drives are sealed and
manufactured in an environment that typically is cleaner than a hospital
operating room. Storage capacity can be increased on both hard disks and floppy
disks with compression programs such as Stacker, WinZip, or PKZIP.
Computer
Software: System Software and Application Software
There are two categories of computer software:
system software and application software. System software serves as the
interface between a user and the computer's hardware. An example of system
software would be an operating system such as Microsoft Windows. Application
software consists of programs designed to perform specific tasks. An example of
application software would be a spreadsheet program, such as Microsoft Excel.
A 3.5-inch floppy disk is computer hardware, but
the programs stored on it are computer software. Although there are two types
of software, system software and application software are designed to work
hand-in-glove; that is, application software packages are designed to work with
specific kinds of system software. By telling the computer how to perform
common functions, the operating system frees application software to
concentrate on producing information. Popular operating systems include
Windows, the Mac OS, OS/2, UNIX, Linux, DOS, and NetWare. Operating systems
that have a graphical user interface (GUI) often are called user-friendly.
Studies have found that GUI users generally complete tasks more accurately,
work faster, are more productive, and feel less fatigue.
To understand the relationship between application software and
system software, draw four concentric circles. Label the innermost circle CPU,
the next operating system, the next application software, and the last user.
The resultant diagram illustrates how the operating system helps to insulate
the user and application program from computer hardware.
Types of
Personal Computer Application Software
Many types of application software are available.
The more popular application software includes word processing software,
electronic spreadsheet software, database software, presentation graphics
software, communications software, and electronic mail software. Knowing the
function of each type of application software is one of the most important ingredients
of being computer literate.
Several years ago, a survey of large and small businesses showed that
the most often used applications were:
- Word
processing and spreadsheet (used by 100% of those surveyed)
- Communications,
electronic mail, database, and presentation graphics (used by about 95%)
- Desktop
publishing (used by about 85%)
- Project
management (used by about 70%)
- Personal
information management (used by about 50%)
In word processing, any work developed
through the writing process is a document. Word processing software makes it
easier to create, edit, format, and print documents. Many word processing
packages include a spell checker, grammar checker, and thesaurus.
The first spreadsheet software, VisiCalc,
was introduced in 1979. By immediately displaying the results of changes,
electronic spreadsheet packages provide a capability called what-if analysis.
Another powerful capability, called goal-seek, finds what value is needed to
reach a specified goal.
A database file is a collection of related
data called records, each of which consists of a group of related facts called
fields. The data can be manipulated, or a report, called a query, can be
created based on user-specified criteria. Although most spreadsheet packages
can manage data tables of a few thousand records, database software can
efficiently handle much larger data tables.
Word processing and spreadsheet software came out
around 1980. Presentation graphics software was not introduced until the mid to
late 1980s. Nevertheless, it can be argued that presentation graphics software
has had almost as great an impact on business, and on how people do business,
as either of the older applications. Presentation graphics packages include
libraries of clip art that can be inserted into slides and a slide sorter that
can be used to organize the order effectively in which slides are presented.
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