CP1610: Introduction to Computer Components The I/O Subsystem: Output Devices

CP1610:Introduction to Computer Components

The I/O Subsystem:

Output Devices

Output Device Topics

Characteristics of Common Output Devices

Characteristics of Common Printer Types VGA and SVGA Monitors Factors that Influence Video Card Quality Factors that Influence Monitor Quality

Printers

A printer is perhaps the second most common output device.

It is used to print output in the form of text or graphics onto a sheet of paper.

Plotters A plotter is a specialized form of printer,

used for printing blueprints and schematics on larger sheets of paper.

Plotters are typically used for engineering and / or architectural applications.

Sound Boards

Sound boards, or sound cards, are used to convert digital data from the computer into signals that can be interpreted, and produced by speaker systems.

Monitors Monitors are the most popular

form of output device. They are used to graphically

display information on a screen for the user, so that the user can monitor the progress of computer programs, and interact with applications and modern operating system interfaces, such as GUI’s (Graphical User Interfaces).

Video Cards

Video cards serve a similar purpose to sound boards.

They are output devices that convert digital data into information that can be used to communicate with either a monitor or an overhead projection device.

This information is then used by the monitor or projector to produce images.

Overhead Projectors An overhead projection system serves the same basic

purpose as a monitor. It produces an image that represents that user’s interaction with the computer system.

The difference is that instead of producing the image on a fixed screen, it projects the image onto a large screen, wall, or other suitable surface.

Such projection systems are popular in business board rooms, classrooms, and even movie theatres.

They are now becoming more popular for home use in connection with DVD players, or computerized home entertainment systems.

Characteristics of Printers

Quality Speed Cost Cost per Page

Cost per Replacement Cartridge

Dot Matrix

Low quality. Produces a series of dots on a page.(70 – 360 dpi)

Some models, such as the Epson LX300+ can achieve printing speeds of 337 characters per second.

Range from $40 -

$3,500

0.1 - 0.2 cents per page

$5 - $20




Ink Jet Can be very high quality.(240/240to1200/1200 dpi)

20 – 40 pages per minute.

Range from $30 -

$3,000

2 – 30 cents per page

$30 - $100




Laser Can be very high quality.(300/300to2400/2400 dpi)

10 – 30 pages per minute

$200 - 8,000

1 - 3 cents per page

$100 - $300




Color Laser

Can be very high quality.(300/300to2400/2400 dpi)


$2000 - $8,000

3 - 9 cents per page

$200 - $600

Characteristics of PrintersQuality Speed Cost Cost per Page Cost per

Replacement Cartridge

Dot Matrix Low quality. Produces a series of dots on a page.(70 – 360 dpi)

Some models, such as the Epson LX300+ can achieve printing speeds of 337 characters per second.

Range from $40 - $3,500

0.1 - 0.2 cents per page

$5 - $20

Ink Jet Can be very high quality.(240/240to1200/1200 dpi)

20 – 40 pages per minute.

$30 - $3,000 2 – 30 cents per page

$30 - $100

Laser Can be very high quality.(300/300to2400/2400 dpi)


$200 - 8,000 1 - 3 cents per page $100 - $300

Colour Laser Can be very high quality.(300/300to2400/2400 dpi)


$2000 - $8,000 3 - 9 cents per page $200 - $600

VGA Monitors Abbreviation of video graphics array, a graphics

display system for PCs developed by IBM. VGA has become one of the de facto standards

for PCs. In text mode, VGA systems provide a resolution

of 720 by 400 pixels. In graphics mode, the resolution is either 640 by

480 (with 16 colors) or 320 by 200 (with 256 colors).

The total palette of colors is 262,144.

SVGA Monitors Short for Super VGA, a set of graphics standards

designed to offer greater resolution than VGA. SVGA supports 800 x 600 resolution, or 480,000 pixels. The SVGA standard supports a palette of 16 million

colors, but the number of colors that can be displayed simultaneously is limited by the amount of video memory installed in a system.

One SVGA system might display only 256 simultaneous colors while another displays the entire palette of 16 million colors.

Factors that InfluenceVideo Card Quality: Memory # of bits / # of colours Refresh Rate Resolution

Memory and Video Card Quality

Many video cards have their own RAM memory, so that the system’s RAM does not need to be tied up with the processing of graphics for the monitor / projector.

The more built-in memory a video card has, the higher quality the card will be, because it will be able to store and process more video data, and do it more quickly.

# of bits / # of colors, and Video Card Quality The amount of information that is stored

about a pixel determines its color depth, which controls how precisely the pixel's color can be specified.

This is also sometimes called the bit depth, because the precision of color depth is specified in bits.

The more bits that are used per pixel, the finer the color detail of the image.

However, increased color depths also require significantly more memory for storage of the image, and also more data for the video card to process, which reduces the possible maximum refresh rate.

The number of colours that can be displayed is a function of the number of bits, or the bit depth. A 4-bit video card can display only 16 colours, an 8-bit

card can display 256 colours a 16-bit card can display over 65-thousand colours,

and a 24-bit card can display over 16-million colours.

Refresh Rate andVideo Card Quality The refresh rate is the number of times per second that

the video card is able to send a signal with image data to the monitor, and the monitor is able to ‘re-paint’ the image on the screen.

The higher the refresh rate, the better the quality of the video card.

Lower refresh rates can actually be problematic for users. A monitor with a low refresh rate may not actually be

visible to the human eye, but your brain can detect the difference – and this can lead to headaches, dizziness, and even migraines.

Resolution and Video Card Quality

Resolution refers to the number of pixels that comprise an image on the screen.

The higher the resolution, the greater the number of pixels that can be displayed, and the smaller the pixels will be.

Hence, the higher the resolution that the video card is capable of outputting, the higher the quality of the card.

(Of course, you may need to reduce the resolution actually being displayed, if the monitor itself cannot handle a resolution that high, or if the monitor is too small to distinguish the details being displayed.)

Factors that InfluenceMonitor Quality Refresh Rate Resolution Dot-Pitch Interlacing Multisync

Refresh Rate and Monitor Quality The refresh rate is the number of times per second that

the video card is able to send a signal with image data to the monitor, and the monitor is able to ‘re-paint’ the image on the screen.

The higher the refresh rate, the better the quality of the video card.

Lower refresh rates can actually be problematic for users. A monitor with a low refresh rate may not actually be

visible to the human eye, but your brain can detect the difference – and this can lead to headaches, dizziness, and even migraines.

Resolution and Monitor Quality Resolution refers to the number of pixels

that comprise an image on the screen. The higher the resolution, the greater the

number of pixels that can be displayed, and the smaller the pixels will be.

Hence, the higher the resolution that the monitor is capable of outputting, the higher the quality of the monitor.

However, just because a monitor is capable of displaying a higher resolution, does not always make it desirable to use the highest resolution setting.

The higher you set the screen resolution, the smaller the images on the screen will be, and the more difficult it will be to distinguish details.

This can really be a problem with smaller monitors.

Dot-Pitch and Monitor Quality Also called phosphor pitch, a measurement that

indicates the diagonal distance between like-colored phosphor dots on a display screen.

Measured in millimeters, the dot pitch is one of the principal characteristics that determines the quality of display monitors.

The lower the number, the crisper the image. The dot pitch of color monitors for personal

computers ranges from about 0.15 mm to 0.30 mm.

Interlacing and Monitor Quality Refresh rates are normally specified for non-interlaced

operation, since that is what modern video systems typically use.

Some older monitors can only display some of the higher resolutions when using interlacing.

Interlacing allows the refresh rate to be double what it normally would be, by displaying alternating lines on each refresh.

In essence, half the screen is redrawn at a time. Interlaced operation is normally done at 87 Hz (really 43.5

Hz because of the interlacing) and hence produces flicker that is noticeable by most people.

Multisync and Monitor Quality A type of monitor that automatically adjusts to the

signal frequency of the video display board to which it is connected.

Consequently, multiscanning monitors can display images based on almost any graphics display system.

Multiscanning monitors scan the incoming signals and set themselves to whatever frequency range they are receiving.

This is in contrast to other types of monitors, which will only function with a limited number of video cards or video modes.

Documents

CP1610: Introduction to Computer Components The I/O Subsystem: Output Devices