Q21969: SCREEN 1 COLOR Yellow Is Brown (Muddy) on EGA Versus CGA Card

Article: Q21969
Product(s): See article
Version(s): 2.00 2.01 3.00 4.00 4.00b 4.50
Operating System(s): MS-DOS
Keyword(s): ENDUSER | | mspl13_basic
Last Modified: 11-JAN-1990

The following program, which uses the COLOR statement on SCREEN 1, may
give different colors on a machine with an EGA card compared to the
colors on a machine equipped with a CGA card:

   10 SCREEN 1
   20 COLOR 8,0
   30 LINE (30,100)-(40,150),3,bf
   40 LINE (10,40)-(60,100),2,bf
   50 LINE (100,100)-(130,130),1,bf

The background color selected is dark gray (8). Palette 0 is selected,
and includes red, green, and yellow on a CGA. Under QuickBASIC on an
EGA card, the colors may appear "muddy" compared to running on a CGA
card: the red and green are less intense than shown on a CGA card and
the yellow is brown.

This is not a problem with QuickBASIC, but is a difference between CGA
and EGA cards. The EGA allows only nonintensified colors. The same
colors occur on an EGA card in the Microsoft GW-BASIC Version 3.20,
3.22, or 3.23 Interpreter on an EGA card.

Note that in SCREEN 1 on an EGA or VGA, the PALETTE statement can
change the color used by output from the PRINT statement, for example

   PALETTE 3,n

where n can be a color from 0 to 15. On an EGA card, PALETTE 3,6
(where 6 is brown) is the default. PALETTE 3,14 will make PRINT output
appear in yellow.

The PALETTE statement is not supported on CGA cards. On a CGA card,
the color of text output with the PRINT statement can only be changed to
one of two possible colors by changing the palette argument of the
COLOR statement. For example

   COLOR b,p

where b is the background color, and p (the palette) can be 0 or 1. If
the p argument is 0, PRINT output displays in color number 6 (brown on
an EGA, yellow on some CGA cards). If the p argument is 1, PRINT
output displays in color number 7 (white). See the COLOR statement in
the BASIC language reference documentation for more information.

Graphics statements such as LINE and CIRCLE can use color (attribute)
arguments 0, 1, 2, or 3 to allow simultaneous display of four colors
at once (including the background) in SCREEN 1 on CGA, EGA, or VGA.

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