ALTAIR 8800 micro Users Manual
© Briel Computers 2010 page 32
Chapter 9: On screen graphics and color
While the VGA monitor gives us a nice crisp 80 column display, it only has the ability to display a single color
of text on the screen at a time. The composite TV output however has the ability to have a different color for
any character on the screen. This gives the user the ability to create simple low resolution color graphics on the
display.
The VT100 control codes can be used in BASIC to not only change text colors but to locate the cursor
anywhere on the screen or clear the screen.
Example:
10 REM CHANGE TEXT COLOR WITH CHOICE OF 1-22
20 REM WE WILL USE COLOR #3
30 PRINT CHR$(27)+”[3T”
40 REM CLEAR THE SCREEN
50 PRINT CHR$(27)+”[2J”
60 REM MOVE THE CURSOR HOME UPPER LEFT
70 PRINT CHR$(27)+”[H”;
80 REM MOVE CURSOR TO Y,X ON A SCREEN OF 40 BY 25 ON TV
90 PRINT CHR$(27)+”[12,20H”;
100 REM PRINT AN X ON THE MIDDLE OF THE SCREEN
110 PRINT “X”;
120 END
This is just a small sample of using VT100 commands to put characters where you want on your screen. Please
refer to Appendix D for a full listing of VT100 codes.
Keyboard function keys:
The Altair 8800 micro terminal section utilizes function keys F1-F5 for special features. This is the list of
features:
CTRL-F1 SEND A TEXT FILE TO BASIC
CTRL-F2 CHANGES TEXT COLOR (HOLD FOR CHANGE)
CTRL-F3 UPDATE TERMINAL FIRMWARE
CTRL-F4 TURNS ON/OFF BACKSPACE MODE*
CTRL-F5 CHANGE CURSOR TYPE BLOCK, UNDERSCORE, BLINKING
* Altair BASIC uses _ to simulate a backspace. The Altair 8800 micro terminal uses the backspace key to
simulate this function. You can turn it on/off with CTRL-F4.
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