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When PC's were in their infancy running under MS-DOS they
only displayed text in one size and one color. Most of those early monitors
were outgrowths of dumb terminals and had green or amber displays on a black
background but for dramatic effect it could be reversed. They ran in two
modes: Text and graphic. In graphic mode a program had to light up (turn on)
each pixel. The screen was 640 pixels wide and 480 high so to clear the
screen in graphics mode a program had to turn off 307200 pixels.
Text on those early PC's was displayed using the ASCII
charter set which was a series of 2 numbers that could be sent to the
monitor. Each of those two digit numbers represented an alpha-numerical
character. For example, the ASCII character code for a lower case a is 97
while the uppercase is 65. A text charter was 8 pixels high and 8 pixels
wide so when a program sent a character 65 to the screen a helper
systems program called ANSI.SYS would send a signal to the proper location
turning on and off 64 dots appropriately to make an image of the letter A.
The 8 by 8 matrix made the screen 80 characters wide
and 60 charters high. To clear the screen only 4800 characters had to be
cleared and only two digits had to be sent for each character. Had the
processors been as fast as they are today everything could have been painted
in graphics mode but they were slow and charter based programs were the
standard.
The first color monitors had multiple size modes which
made it possible to display larger text (still using the ASCII system) but
the whole screen had to be shifted to the larger text. The first version of
Windows was awful, especially when you compared it to the Mac or the
Commodore Amiga simply because the PC's ability to display graphics was
inferior but as clock speeds and processing power increased so did the
quality of Windows. Windows and other graphical operating systems, used a
font (a miniature picture) to paint text on the screen in graphical mode.
The system is similar to the ASCII concept. Now the program specified the
font and the charter.
The full evolution of text was the vector based, true
type, proportional font introduced by Adobe which was as smart as a skilled
typesetter. It was Adobe's early efforts at creating graphics based fonts
that put them into the imaging business.
- If you know all about formatting text, skip the
Exercises and go to the Next lesson.
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