3. Monitors
A monitor is a peripheral device which displays computer
output on a screen.
Screen output is referred to as soft copy.
Types of monitors:
Cathode-ray tube (CRT)
Liquid Crystal Display (LCD or flat-panel)
Light-emitting Diode (LED)
3
CRT
LCD
4. Monitors - CRT Monitors
• In CRT monitors, electrons are fired at phosphor
dots on the screen.
• The dots are grouped into pixels, which glow when
struck by electrons.
• In color CRTs, each pixel contains a red, green, and
blue dot.
• These glow at varying intensities to produce color
images.
6. Monitors - Flat-Panel Monitors
• Most flat-panel monitors use Liquid Crystal Display
(LCD) technology.
• Passive matrix LCD uses a transistor for each row and
column of pixels. The color displayed by a pixel is
determined by the electricity coming from the transistor.
• Active matrix LCD uses a transistor for each pixel on the
screen.
• Thin-film transistor (TFT) displays use multiple
transistors for each pixel.
• TV sets are CRTs and many desktop monitors use this
technology
• LCD is primarily used for laptops and other portable devices
10. Comparing Monitors - Size
Screen size – The diagonal measurement of the screen surface in inches (15,
17, 19, 21)
The diagonal
size (often 15”)
11. Comparing Monitors - Resolution
• Resolution is the number of pixels on the screen, expressed as a
matrix (such as 600x800).
• It is the image sharpness of a display screen.
• It is expressed as a matrix.
• A resolution of 640x480 means there are 640 horizontal pixels and
480 vertical pixels.
• Most monitors provide the resolution 640x480, 800x600 and
1024x768
13. Comparing Monitors - Refresh
Rate
• Refresh rate – The speed at which the screen is redrawn
(refreshed).
• Refresh rate is the number of times each second that
the electron guns scan the screen's pixels.
• Refresh rate is important because phosphor dots fade quickly
after the electron gun charges them with electrons.
• Refresh rate is measured in Hertz (Hz), or cycles per second.
15. Comparing Monitors - Dot Pitch
• The distance between the phosphorus dots create a single pixel is called dot pitch.
• Dot pitch is the distance between the like-colored phosphor dots of adjacent
pixels.
• In other words, if you measure the distance between the red dots of two adjacent
pixels, you are measuring the monitor’s dot pitch.
• In color monitors, three dots (red, green, and blue) comprise each pixel.
• Look for a dot pitch no greater than .28 millimeter.
16. R + BB + G
R + G
R + B + G
Phosphor Dot Color Mixing
18. Printers
A printer is a peripheral device that produces a physical copy or hard copy
of the computer’s output.
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19. Overview of Printers
Categorizing Printers
Printers fall into two categories:
1. Impact Printers
2. Non Impact Printers
Impact printers creates an image by using pins or hammers to
press an inked ribbon against the paper.
A simple example of impact printer is a type-writer, which uses small hammers to
strike the ribbon.
Each hammer is embossed with the shape of a letter, number or symbol; that shape is
transferred through the inked ribbon onto the paper, creating a printed character.
The most common type of impact printer is the “dot matrix printer”.
Another example of impact printer is line printers
20. Overview of Printers - Categorizing
Printers
Printers fall into two categories:
Non-impact printer prints character and graphics on a piece of paper without
striking the paper.
Non-impact printers use different methods to place ink (or another substance) on
the page.
Ink jet printers, for example, use tiny nozzles to spray droplets of ink onto the
page.
Laser printers work like photocopiers, using heat to bond microscopic particles
of dry toner to specific parts of the page.
21. Overview of Printers - Evaluating
Printers
When evaluating printers, consider four criteria:
Image quality – Measured in dots per inch (dpi). Most printers
produce 300 – 600 dpi.
Speed – Measured in pages per minute (ppm) or
characters per second (cps).
Initial cost – Consumer printers cost $250 or less, but
professional printers can cost thousands of dollars.
Cost of operation – This refers to the cost of supplies used by the
printer.
22. Dot Matrix Printers -
How Do Dot Matrix Printers Work?
A dot matrix printer is the example of impact printer
A dot matrix creates an image by using a mechanism called a “print head”,
which contains a cluster (or matrix) of short pins arranged in one or more
columns.
On receiving instructions from PC, the printer can push any of the pins out in
any combination.
The protruding pins’ end strike a ribbon, which is held between the print head
and paper.
When the pins strike the ribbon, they press ink from the ribbon onto the paper.
24. Dot Matrix Printers - Performance
Lower-resolution dot matrix printers use nine pins. Higher-resolution models
have 24 pins.
Speed is measured in characters per second (cps). Some dot matrix
printers print 500 cps.
25. Ink Jet Printers –
How Do Ink Jet Printers Work?
Ink jet printers are an example of non-impact printers.
The printer sprays tiny droplets of ink onto the paper.
Ink jet printers are available for color and black-and-white printing.
Color ink jet printers have four ink nozzles: cyan (blue), magenta (red), yellow
and black. (CMYK printers)
Printed color is the result of light bouncing off the paper, not color transmitted
directly from a light source.
• A stepper motor moves the print head assembly (print head and ink cartridges)
back and forth across the paper.
27. Ink Jet Printers - Performance
Ink jet printers offer speeds of (2 – 4 pages per minute ppm) and resolution (300 –
600 dots per inch dpi), comparable to low-end laser printers.
Ink jet printers are inexpensive and have low operating costs.
28. Laser Printers –
How Do Laser Printers Work?
Laser printers are non-impact printers with a laser at the
heart of these printers.
• Just as the electron gun in a monitor can target any pixel, the laser in a laser
printer can aim at any point on a drum,creating an electrical charge.
A CPU and memory are built into the printer to interpret the data that it received
from the computer and to control the laser.
They use heat and pressure to bond particles of toner to paper.
Laser printers are available for color and black-and-white printing.
30. Laser Printers - Performance
Laser printers provide resolutions from 300 – 1200 dpi and
higher.
Black-and-white laser printers usually produce 4 – 16 ppm.
Laser printers produce higher-quality print than ink jet printers, but are more
expensive.
31. Other Types of Printers
Photo Printers
• Photo printers are specialized, small-format printers
that print digital photographs.
• Photo printers are fairly slow, and can be more
expensive to operate
• Many photo printers use ink jet technology.
• One advantage of the newest photo printers is that
they don’t need a computer. These printers feature
slots for memory cards used by many digital cameras.
Photo printers are popular among
digital camera users
32. Other Types of Printers
A multifunction peripheral (MFP) is a single device that prints, scans, copies, and in some cases,
faxes
Sometimes called an all-in-one device
33. Other Types of Printers
A thermal printer generates images by pushing electrically heated pins against the heat-sensitive
paper
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Thermal wax-transfer printer
Dye-sublimation printer
34. Plotters
A plotter is specialized output device. It is designed to produce
image-quality graphic in a variety of colors and size.
Plotters are used to create maps, architectural drawings and 3-D
illustration.
A plotter works by drawing lines on paper using pens held in
mechanical arm
36. Other Output Devices
Headphones are speakers
that cover your head or are
placed outside of the ear
Earbuds (also called
earphones) rest inside the ear
canal
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37. Other Output Devices
A data projector or PC
projector is a device that
takes the text and images
displaying on a computer
screen and projects them on a
larger screen
Many PC projectors provide
the same resolutions and
color levels as high-quality
monitors.
Digital light processing (DLP)
projectors use a microchip
containing tiny mirrors to
produce very sharp, bright
images.
