IT
POINTERS FOR MIDTERMS
INPUT DEVICE
Input refers to data entered into a computer for
processing— for example, from a keyboard or
from a file stored on disk. Input includes program
instructions that the CPU receives after
commands are issued by the user.
Input hardware consists of devices that translate
data into a form the computer can process. The
people-readable form of the data may be words
like those on this page, but the computer
readable form consists of binary 0s and 1s, or off
and on electrical signals.
What are the three categories of input hardware,
what devices do they include, and what are their
features?
1. KEYBOARDS - is a device that converts letters,
numbers, and other characters into electrical signals
that can be read by the computer’s processor. The
keyboard does this with its own processor and a grid
of circuits underneath the keys.
Traditional Computer Keyboards. Conventional
computer keyboards have all the keys on old
typewriter keyboards, plus other keys unique to
computers. This generally totals 104–108 keys for
desktop computers and 80–85 keys for laptops.
Wired keyboards connect a cable to the
computer via a serial port or a USB port.
Wireless keyboards use either infrared-light (IR)
technology or radio frequency (RF) technology to
transmit signals to a receiver device plugged into the
computer, usually via a USB port. Infrared wireless
keyboards have a transmission range of 6–10 feet
and cannot have any obstacles in the transmission
path (called the line of sight).
Virtual Keyboard. The size of a writing pen, it
uses light (laser) to project a full-size computer
keyboard onto almost any surface; the image
disappears when not in use.
Specialty Keyboards and Terminals
a) Dumb Terminals - A dumb terminal, also
called a video display terminal (VDT), has a display
screen and a keyboard and can input and output but
cannot process data. Usually the output is text only.
b) Intelligent Terminals - An intelligent terminal
has its own memory and processor, as well as a
display screen and a keyboard. Such a terminal can
perform some functions independent of any
mainframe to which it is linked. (ex: ATM, POS)
c) Internet Terminals - An internet terminal
provides access to the internet —that is, it powers up
directly into a browser.
2. POINTING DEVICE - control the position of the
cursor or pointer on the screen and allow the user to
select options displayed on the screen.
The Mouse. The principal pointing tool used with
microcomputers is the mouse, a device that is rolled
about on a desktop mouse pad and directs a pointer
on the computer’s display screen.
Variations of Mouse
a) Trackball - The trackball is a movable ball,
mounted on top of a stationary device, that can be
rotated using your fingers or palm.
b) Pointing Stick - A pointing stick looks like a
pencil eraser protruding from the keyboard between
the G, H, and B keys.
c) Touchpad - A touchpad is a small, flat surface
over which you slide your finger, using the same
movements as you would with a mouse. The cursor
follows the movement of your finger.
3. TOUCHSCREEN - is a video display screen that
has been sensitized to receive input from the touch
of a finger.
4. PEN INPUT
Pen-based computer systems: Pen-based
computer systems allow users to enter handwriting
and marks onto a computer screen by means of a
pen-like stylus rather than by typing on a keyboard.
Stylus is a pen-like device that is used to write
text or draw lines on a touch sensitive surface as
input to a computer.
Handwriting recognition refers to the ability of a
computer to receive intelligible written input. The
system requires special software that interprets the
movements of the stylus across the writing surface
and translates the resulting cursive writing into
digital information.
Light pen: The light pen is a light-sensitive pen-
like device that uses a wired connection to a
computer terminal. The user brings the pen to a
desired point on the display screen and presses the
pen button, which identifies that screen location to
the computer.
Digitizer: A digitizer uses an electronic pen or a
mouse-like copying device called a puck that can
convert drawings and photos to digital data. One
form of digitizer is the digitizing tablet, used in
engineering and architecture applications, in which a
specific location on an electronic plastic board
corresponds to a location on the screen.
Digital pen: A digital pen is a writing instrument
that allows users to write on paper and send the
writing as an image file to the computer.
5. SCANNING & READING DEVICES
Source data-entry devices create machine-
readable data on magnetic media or paper or feed it
directly into the computer’s processor.
SCANNERS. Scanners, or optical scanners, use
light-sensing (optical) equipment to translate images
of text, drawings, photos, and the like into digital
form.
Bar-code readers are photoelectric (optical)
scanners that translate the symbols in the barcode
into digital code.
