Computer Fundamentals

MSCH 233

Lecture 5

The Monitor

A Monitor is a video screen that looks like a TV. It displays both the input data and instructions, computer responses, and output information.

Early PC Monitors or screens were usually either black and white or black and green, but today’s monitors can produce high-quality graphics in many colors.

Pixels & Resolution

Every character you see on the screen are made up of dots called Pixels ( picture element).

The quality of what you see on the screen is determined by how many pixels your monitor displays. The more pixels, the better the resolution, or crispness, of the character on the screen.

Early models consist of 640 X 480 pixels; more recent models today have 1024 X 768 pixels.

Type of Monitors

CRT Monitor Monochrome Monitors Colored Monitors

Flat Panel Liquid-Crystal Display (LCD)

CRT ( Cathode Ray Tube) Monitors

Inside the Monitor Tube is an electron beam which scans the screen and turns the pixels on and off to make up the picture.

The electron beam scans the screen from the top left to the right. The sequence is repeated 50, 70 or 85 times per second depending on the system.

If the “refresh rate” of the scanning is low , we can see a flickering, unsteady screen. However a fast moving 75 Hz eliminates this annoying flickering.

What we see in the screen is created and stored in the RAM. So there is a memory cell allocated to each pixel. This type of display is called bit-mapped.

Monochrome Monitors

Displays only one color , and it is typically green or white against black background.

Bits 0 are visualized as white or green dots , and bit 1 as black dots.

Colored CRT Monitors

There are three electron beams Each tube shoots out beam of electron for

each primary colors: red, green, blue. The screen is coated with substance

called Phosphor that glow when struck by electrons

It uses 3 different phosphor materials.The intensity of each of the three electron

beams is varied to create different colors.

VGA ( Video Graphic Adapter)

VGA Cards is a display adapter, which plugs into the motherboard of a computer.

It became a standard display adapter for colored monitors.

Their resolution is 1024 X 768 pixels and more.

It can display 64K, 256 k, and 16.7 million colors

Flat-Panel LCD

Uses Liquid-crystal display instead of a picture tube.

It uses crystals and two sheets of polarized filters. The crystals block the light in different amounts to generate the dots in the image.

Advantage: Require less space Five crisp clear images Eliminates screen flicker.

Advice when using a computer

Do not stare at the screen for long period of time Avoid placing the monitor so that is reflects a source of bright light ,

such as a window. Keep the screen clean to prevent distorting shadows. Don’t set too close to the side or back of the monitor Buy a protective filter that cuts down ELF( extremely low frequency)

emissions. Position your keyboard at the same height as your elbow. Take a break from the computer at least every twenty minutes and

do some simple stretching to relieve the muscles they have been using.

Your back should be supported in an upright position in the chair and you body should face forwards not twisted sideways.

Thanks You