Chapter 2: Looking At Computers
A computer is a data processing device, which perform 4 major functions.
1. Gathers data and allows users to input data.
2. Processes that data into information.
3. Outputs data and information
4. Stores data and information
In computer terms:
Data is a representation of a fact, figure, or an idea. ex. number, word, picture,
Information is data that has been organized or presented in a meaningful fashion. ex.
When your computer provides you with a contact listing Joe Brown can be reached
by phone at (713) 555-3297
Computers communicate in binary language, which consists of “0’s” and “1’s”, each
0 and 1 is a binary digit or bit for short. 8 bits combine to equal one byte. Each letter
of the alphabet, number, special character “&”, consist of 8 bits or a byte.
These “bits” and “bytes” are used as a language to tell the computer what to do as
well as representing data and information that it inputs and outputs.
Page 49, Figure 2.2 of your textbook shows different sizes and types of “bytes”.
Your computer uses a combination of hardware and software to process data into
information and enables you to complete tasks such as writing a letter or playing a
game. Hardware is any part of the computer you can physically touch. Software is
the set of computer programs that enables the hardware to perform different tasks;
two types of software are application software and system software. Application
software is the set of programs you use on a computer to help you carry out tasks
such as writing a research paper if you’ve ever typed a document, created a
spreadsheet, or edited a digital photo. System software is the set of programs that
enables your computer’s hardware devices and application software to work
together, most common type of system software is the operating system (OS). The
OS controls the way in which our computer system functions.
There are two basic designs of computers: portable and stationary
A notebook or laptop is a portable computer that is powered by batteries and has a
keyboard, monitor, and other devices integrated into a single compact case. A
netbook is a small, lightweight notebook computer that is generally 6 to 10 inches
wide and has a longer battery life than a notebook but features a touch sensitive
screen that can swivel and fold flat. A desktop computer is intended for use at a single location, and therefore, is
stationary. Desktop computers consist of a separate case that houses the main
components of the computer plus peripheral devices. A peripheral device is a
component of the computer such as a monitor or keyboard.
A mainframe is a large, expensive computer that supports hundreds of users
simultaneously. Mainframes are often used in insurance companies, for example,
where many people are working on similar operations (such as claims processing)
all at once.
A supercomputer is a specially designed computer than can perform complex
calculations extremely rapidly. Supercomputers are used in situations in which
complex models requiring intensive mathematical calculations are needed (weather
forecasting and atomic energy research). Main difference between a supercomputer
and a mainframe is that supercomputers are designed to execute a few programs as
quickly as possible, mainframes are designed to handle many programs running at
the same time but at a slower pace.
An embedded computer is a specially designed computer chip that resides in
another device such as your car or the electronic thermostat in your home. They are
self-contained computer devices that have their own programming and typically do
not receive input from you or interact with other systems.
An input device enables you to enter data (text, images, and sounds) and
instructions (user responses and commands) into the computer. Examples of input
devices would be keyboard, mouse, and stylus.
Most desktops and notebooks come with the standard QWERTY keyboard we see
everywhere, this name was given by the first six letters at the top left of the
keyboard in that same order. Another type of keyboard is the Dvorak keyboard, this
keyboard has not met with much public interest and is used as an alternative
keyboard layout that puts the most commonly used letters in the English language
on “home keys” which are they keys in the middle row of the keyboard. Used to
reduce distance of finger travel and increased typing speed.
Pg. 54 demonstrates all commands involving shortcuts using the control key
combined with another letter for windows operating systems.
Touch Screens are display screens that respond to commands initiated by a touch
with a finger or a stylus, which happen to be increasingly popular on many
Output devices allow you to send processed data out of your computer in the form
of text, pictures (graphics), sounds (audio), or video. Common types of output types
are monitors and printers. Two different types of monitors include: liquid crystal display (LCD), Cathode ray
tube (CRT). LCD also known as a flat-panel monitor is a light and energy efficient
monitor. Some use light-emitting diode (LED) technology, which happens to be even
more energy efficient as well as better color accuracy and thinner panels than
tradition LCD monitors. In today’s world, LCD has replaced CRT’s, CRT’s are difficult
to find or buy because they have become legacy technology. Although legacy
technology may still be functional, newer technological advances are quickly
replacing it. LCD monitors are made of two or more sheets of material filled with a
liquid crystal solution; these crystals move around and either block fluorescent light
or let light shine through.
When choosing an LCD monitor two major factors to consider are aspect ration and
resolution. Aspect ratio is the width-to-height proportion of a monitor, traditionally
aspect rations have been 4:3, but newer monitors are available in a 16:9 or 16:10
ratio. The screen resolution, clearness, or sharpness of the image, reflects the
number of pixels on the screen. An LCD monitor may have a resolution of 1,600 x
1,200 meaning it contains 1,600 vertical columns with 1,200 pixels in each column.
The higher the resolution the sharper and clearer the image will be. Resolution is
generally dictated by the screen size and aspect ratio.
Other factors to consider are contrast ratio, viewing angle, brightness, and response
time. Contrast ratio is a measure of the difference in light intensity between the
brightest white and the darkest black that the monitor can produce. If contrast ratio
is too low, colors tend to fade when you adjust brightness to a high or low setting.
Contrast ratio between 400L1 and 1,000:1 is preferable.
Viewing Angle is an LCD’s viewing angle, which is measured in degrees, which tells
you how far you can move to the side of (or above or below) the monitor before the
image quality degrades to unacceptable levels. Monitors that measure 17+ inches, a
viewing angle of at least 150 degrees is recommended.
Brightness is measured as candelas per square meter or nits, brightness is a
measure of the greatest amount of light showing when the monitor is displaying
pure white. A brightness level of 300 candelas per square meter + is recommended.
Response time is a measurement (in milliseconds) of the time it takes for a pixel to
change color. A lower response time value means faster transitions therefore;
moving images will appear less jerky on the monitor.
Monitors are grids made up of millions of tiny dots known as pixels and illuminated
pixels create the images you see on your monitor. Each pixel is comprised of three
sub pixels that are red, blue, and green. Newer TVs in today’s market have even
included a fourth new color: yellow.
If the situation comes up where you have to show output to a large group of people,
your computer monitor is not ideal; in this case you would choose to use a
projector. Which is a device that can project images from your computer on to a
wall or viewing screen, they are commonly used in business and education settings
such as conference rooms and classrooms. Printers – There are two primary categories of printers, inkjet and laser. Both of
which are nonimpact, nonimpact printers spray ink or uses laser beams to transfer
marks onto the paper, today they have replaced impact printers almost entirely.
Impact printers have tiny hammer like keys that strike the paper through an inked
ribbon making marks on the paper. The most common impact printer is the dot-
matrix printer. Inkjet printers are the standard type of printers found in homes,
their popularity comes from the affordability and production of high quality color
printouts quickly and quietly. They work by spraying tiny drops of ink onto paper
and are great for printing black and white text as well as color. Laser printers are
most often used in office or classroom settings because they have a faster printing
speed compared to inkjet printers and produce higher quality printouts. Laser
printers use laser beams and static electricity to deliver toner onto the correct areas
of the page. Recently the quality of laser printers has improved and the prices have
dramatically dropped making them highly price competitive with high-end inkjet
Wireless printers are also offered, allowing several people to print to the same
printer from different places. Two different types of wireless printers are Wi-Fi and
Bluetooth, both Wi-Fi and Bluetooth have a range of up to approximately 300 feet.
However Wi-Fi has the advantage of sending data more quickly than Bluetooth. An
all-in-one printer is a device that combines the functions of a printer, scanner,
copier, and fax into one machine, which use either inkjet or laser technology. A
plotter is another type of printer that produces oversized pictures that require the
drawing of precise and continuous lines, such as maps, detailed images, and
architectural plans. Plotters use a computer-controlled pen that provides a greater
level of precision than the series of dots that laser or inkjet printers possess.
Thermal printers are another type of specialty printer. They work either by
melting wax-based ink onto ordinary paper or by burning dots onto specially coated
Criteria to selecting the best model for your printing needs:
Speed – A printer’s speed determines how many pages it can print per minute
expressed as pages per minute or ppm. The speed of the inkjet printer has improved
over years and many print as fast as laser printers. Printing speeds vary by model
and range from 8 ppm and 38 ppm. Text documents have proven to be print faster
in black and white than documents printed in color.
Resolution – A printer’s resolution is measured in dots per inch, which is the
number of dots of ink in a one-inch line. The higher the dpi, the greater the level of
detail and quality of the image. You’ll sometimes see dpi represented as a horizontal
number by vertical number such as 600 x 600, but you may also see the same
resolution simply slates as 600 dpi. For general-purpose printing, 1,200 dpi is
sufficient. For photo’s 4,800 dpi is better. The dpi for professional printers is twice
of that. Color Output- If you’re using an inkjet printer to print color images, buy a four color
printer (cyan, magenta, yellow, and black) or a six