Information Systems Theory
Chapter 4: Input and Output
This chapter discusses various input and output devices. The objectives
important to this chapter are:
- Understanding four types of input
- Understanding the features of keyboards
- Understanding mice and other pointing devices
- Understanding output, including printed output and
Four bullets on page 4.2 summarize four kinds of input:
- data - raw facts and numbers
- programs - instructions for a computer
- commands - often, the signal to begin, end, or modify the
execution of a program
- user responses - information a program may need to begin or
complete a task
Keyboards are the most common devices used to give input to a computer.
The alphabetic keys are often laid out like a typewriter. Additional keys
are often found on a computer keyboard:
- numeric keypad - a grid of keys resembling those on many calculators,
making numeric entry easier.
- cursor control keys - used to move or position the cursor;
keys such as arrows (left, right, up, and down), line movement (HOME
and END), and page movement (Page Up and Page Down)
- lock keys - three keys to set default behaviors:
- Num Lock - When turned on, this assigns the numeric
keypad to act like number keys. When turned off,
the numeric keypad acts like arrow keys. Which ever
state is in effect, holding a shift key down makes the key
act the other way.
- Caps Lock - When turned on, this locks the alphabetic
keys in Capital Letter mode. When turned off,
the alphabetic keys are locked in Lower Case mode. Again,
whichever state is in effect, pressing a shift key makes
the key act the other way.
- Scroll Lock - When turned on, this is supposed
to lock the cursor in one position on the screen and allow the user
to move the screen instead of the cursor. I have not used this feature
in years. While experimenting for these notes, I could not tell
that it had any effect at all in any software I had handy.
- function keys - these are "extra" keys that are usually assigned
different specific functions in different programs. Large applications
invariably use the keys, they just do different things in different
Pointing devices come in various types:
- mouse - first choice for most users, it may have one or more
- trackball - often integrated into laptop keyboards, sometimes
used by people with limited arm movement
- touchpad - also found on many laptops, sometimes under the
- pointing stick - I have never heard this generic term. This
is actually a small button mounted on a stress gauge, which works as
though it were a real joystick. On an IBM ThinkPad, it is called an
- joystick - the main use of joysticks is in games, usually
flight simulation and combat games
- pen input - used in credit card applications, signature collection,
and on several types of personal assistant devices
- touch screen - often used in kiosk devices, such as informational
terminals in malls and airports
- light pen - used to create and change drawings on a screen
- digitizer - used to scan or trace an existing drawing into
a CAD program
- graphics tablet - used for fine control, and to issue commands
to a CAD program
The next topic is Source Data Automation, which means turning
a source document into an electronic document without some of the manual
labor. Scanners, both handheld and page scanners
(also called flatbed scanners) are shown capturing pictures and
text to be stored in electronic documents.
Three varieties of Optical Recognition are discussed:
- Optical Codes - such as scanning bar codes and price codes
- Optical Marks Recognition - such as scanning answer sheets
for quizzes and surveys
- Optical Character Recognition - such as scanning a printed
document to create an electronic copy
Magnetic Ink Character Recognition (MICR) is a technique that
is used mainly by banks and credit unions to scan information printed
on checks. The check typically has the bank number and account number
printed on it in magnetic ink when the user receives the check. The amount
a check is written for is printed on it later.
Terminals are usually divided into two types. Dumb terminals
do no processing themselves; they only serve to connect to a real
computer elsewhere. Smart terminals connect to another computer,
but they are capable of processing some instructions themselves.
An ATM (Automatic Teller Machine) is given as an example of a smart terminal.
It is capable of processing a simple request for a user (like a twenty
dollar withdrawal) even if it can't contact the bank's mainframe at the
There are many types of output. The first types discussed on
page 4.23 are types of reports:
- internal reports - these are distributed within an organization
- external reports - these are given to people outside the organization
that produces the reports
- detail reports - typically, there will be a line in the report
for every item in a list, such as a line for every item in an
- summary reports - these may summarize information from detail
reports, such as reporting only the total number of items in
each warehouse, instead of listing each item
- exception reports - these report only unusual items,
such as a list of broken items in a warehouse, instead of all items
Display output is associated with several terms:
- CRT - a Cathode Ray Tube, or sometimes just tube,
is another name for a computer monitor
- screen - this word may be used to mean the monitor
itself, or the current layout of information being shown
on a monitor
- monochrome - a monitor that displays only one color
(on a black background) is a monochrome monitor. They are usually green
- gray scale - this is a method of displaying pictures on a
monochrome monitor using different brightnesses and intensities of the
single color to simulate more color depth. An example is a black and
white television, which uses a lot of shades of gray.
- liquid crystal display - a flat panel, often found as a display
screen in a laptop computer. Two types are common: passive matrix,
which is cheaper and consumes less power, and active matrix,
which is brighter (as well as more expensive).
- pixel - a pixel is another contraction, standing for "picture
element". It is one of the "dots" that a monitor's picture is made of.
- resolution - this is the density of pixels that a monitor
can display. Often, monitors can display several densities: VGA
resolution is 640 by 480 pixels, while SVGA resolutions
include 800 by 600 and 1024 by 768 pixels.
- dot pitch - this is the distance from the center of one pixel
to the center of the nearest pixel on a monitor. Smaller numbers are
better. A typical acceptable value for dot pitch is .28 millimeters.
.15 would be excellent, .39 would be very grainy.
Printers come in several types:
- impact printers - something has to hit something to make the
output. A dot matrix printer has a series of pins that
hit a ribbon to leave a mark on paper. A band printer
has hammers that hit a metal band which is embossed with
characters, and it hits a ribbon, leaving a mark on paper.
- ink jet printers - commonly used in homes and offices, these
printers spray dots of ink onto paper
- laser printers - this technology is similar to a photocopier;
color laser printers are currently expensive to use and own
- thermal printers - these produce high quality output by using
special dye-impregnated transfer sheets to create glossy color images
on output paper
- plotters - most often used for drafting output, such as blueprints
and schematic drawings; able to print to large sheets of paper used
by builders and architects
Projectors currently come in two types:
- projection panel - fits on a standard overhead projector,
a computer sends and image to the panel, the projector shines a light
through the translucent panel, and an image is projected on a wall or
- LCD projector - brighter than overheads, this device resembles
a slide projector. A computer attaches to the device, which uses its
own light to project an image.
Microfilm output is often used when keeping records, such as
legal records that do not need to be edited, only stored.
Facsimile (FAX) machines come in several varieties. A
fax/modem is used to send an image directly from a program
to a fax receiver at another site, giving the user much cleaner output
than is possible by printing, scanning, sending and receiving (as is done
in a traditional fax format).