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Q35148: Underline, Reverse, Intense, Blinking in Monochrome SCREEN 0

Article: Q35148
Product(s): See article
Version(s): 4.00 4.00b 4.50
Operating System(s): MS-DOS
Keyword(s): ENDUSER | B_BasicCom B_GWBasicI | mspl13_basic
Last Modified: 16-DEC-1989

On the Hercules Graphics Adapter (HGA) or the IBM Monochrome Display
Adapter (MDA), the foreground and background arguments of the COLOR
statement support underlined, reverse-video (highlighted), blinking,
or high-intensity characters. Reverse/underline and intense/reverse
combinations are not supported by HGA or MDA.

The following 11 combinations of COLOR statement foreground and
background values are available on monochrome, SCREEN 0 (text)
displays:

   FORMAT                  COLOR Statement       ATTRIBUTE

White on black (normal)       COLOR 7,0              7
Black on black (no display)   COLOR 0,0              0
Black on white (reverse)      COLOR 0,7            112
Underline                     COLOR 1,0              1
Intense                       COLOR 10,0            10
Blinking                      COLOR 18,0           130
Reverse blinking              COLOR 16,7           240
Intense underline             COLOR 9,0              9
Intense blinking              COLOR 26,0           138
Underline blinking            COLOR 17,0           129
Intense blinking underline    COLOR 25,0           137

This information applies to the following products:

1. Microsoft QuickBASIC Compiler Versions 4.00, 4.00b, 4.50

2. Microsoft BASIC Compiler Versions 6.00 and 6.00b for MS-DOS and
   MS OS/2

3. Microsoft BASIC PDS Version 7.00 for MS-DOS and MS OS/2

4. Microsoft GW-BASIC Interpreter Versions 3.20, 3.22, and later

In SCREEN 0 with a color card (CGA, EGA, or VGA), the COLOR statement
is used to change the foreground and background colors that are
displayed. The COLOR statement also lets you select intense or
blinking options for the foreground color. Underlining is not
supported on color monitors.

In text mode (SCREEN 0), two consecutive bytes are used to store each
character in screen memory. One byte contains the ASCII value of a
character, and the following byte contains ATTRIBUTE information for
that character. Attributes can be calculated with the following
formula:

ATTRIBUTE = 128*(FOREGROUND\16)+BACKGROUND*16+(FOREGROUND MOD 16)

[Note: The backslash character (\) is the integer division operator.]

See Pages 79-81 of "The Peter Norton Programmer's Guide to the IBM PC"
(published by Microsoft Press, 1985) for more information about
attributes.

The following book from Microsoft Press describes video details more
completely:

   "Programmer's Guide to PC & PS/2 Video Systems," by Richard Wilton
   (1987). Chapter 3 describes the alphanumeric video modes.

The following is a code example:

'This program will display all of the character formats resulting from
'each of the 32 foreground colors available for any of the 8
'recognized background colors with a monochrome card in SCREEN 0 (text
'mode).

   DEFINT A-Z
5  CLS
   LOCATE 20, 15
   COLOR 7, 0
   liner = 0
   INPUT "background="; back
   FOR fore = 0 TO 31
        IF liner = 16 THEN
                liner = 0
        END IF
        liner = liner + 1
        LOCATE liner, 1 + (20 * (fore \ 16))
        PRINT fore; back;
        COLOR fore, back
        PRINT "A"
        COLOR 7, 0
   NEXT fore
   WHILE INKEY$ = "": WEND
   GOTO 5

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