Toshiba PORTEGE 650CT, Руководство пользователя

Страница: 284 / 458

What’s Really Going On?
How Does the Screen Display Information?
Part I: Getting To Know Your Computer
297
Displaying Colors
The pel size also determines how many colors the display can pro-
duce. By combining pixels of different colors within a pel, the dis-
play can produce many more colors than are available within a
single pixel. Therefore, larger individual pels increase the number
of colors available to the display.
Video Modes
Video modes are sets of industry-standard rules about resolution
and the maximum number of distinct colors that can be displayed
simultaneously on the screen. Programs that adhere to the rules of
a video mode will run on any system that supports that mode.
Most display adapters provide several video modes. The Portégé
650CT SVGA-compatible display adapter supports all VGA
modes and some SVGA modes.
The video mode required by a program depends on:
❖
whether the program displays graphics or text.
❖
the resolution required for the text or graphics.
❖
the number of colors used.
❖
the font size (in pixels) of the text.
Based on these requirements, computers recognize two categories
of video modes: graphics modes and text modes.
In a graphics mode, programs can turn on and off individual pels
to display a variety of images. The computer controls every pel on
the screen individually. This provides maximum display flexibil-
ity while somewhat reducing the speed at which the display pro-
duces images.
An image produced this way could be a drawing or picture, like a
pie chart, graph or photograph. It could also be an icon or a varia-
tion on a text character, like italics or bold type.