Basic computer language commands

Basic computer programming language

PALETTE, PALETTE USING Statements

Purpose:

Changes one or more of the colors in the palette

Syntax:

PALETTE [attribute,color]
PALETTE USING integer-array-name (arrayindex)

Comments:

The PALETTE statement works only for systems equipped with the IBM® Enhanced Graphics Adapter (EGA). A GW-BASIC palette contains a set of colors, with each color specified by an attribute. Each attribute is paired with an actual display color. This color determines the actual visual color on the screen, and is dependent on the setting of your screen mode and your actual physical hardware display.

PALETTE with no arguments sets the palette to a known initial setting. This setting is the same as the setting when colors are first initialized.

If arguments are specified, color will be displayed whenever attribute is specified in any statement that specifies a color. Any color changes on the screen occur immediately. Note that when graphics statements use color arguments, they are actually referring to attributes and not actual colors. PALETTE pairs attributes with actual colors.

For example, assume that the current palette consists of colors 0, 1, 2, and 3. The following DRAW statement:

DRAW "C3L100"

selects attribute 3, and draws a line of 100 pixels using the color associated with the attribute 3, in this case, also 3. If the statement:

PALETTE 3,2

is executed, then the color associated with attribute 3 is changed to color 2. All text or graphics currently displayed on the screen using attribute 3 are instantaneously changed to color 2. All text or graphics subsequently displayed with attribute 3 will also be displayed in color 2. The new palette of colors will contain 0, 1, 2, and 2.

With the USING option, all entries in the palette can be modified in one PALETTE statement. The integer-array-name argument is the name of an integer array, and the arrayindex specifies the index of the first array element in the integer-array-name to use in setting your palette. Each attribute in the palette is assigned a corresponding color from this integer array. The array must be dimensioned large enough to set all the palette entries after arrayindex. For example, if you are assigning colors to all 16 attributes, and the index of the first array element given in your PALETTE USING statement is 5, then the array must be dimensioned to hold at least 20 elements (since the number of elements from 5-20, inclusive, is 16):

DIM PAL%(20)
.
.
.
PALETTE USING PAL%(5)

If the color argument in an array entry is -1, then the mapping for the associated attribute is not changed. All other negative numbers are illegal values for color.

You can use the color argument in the COLOR statement to set the default text color. (Remember that color arguments in other BASIC statements are actually what are called attributes in this discussion.) This color argument specifies the way that text characters appear on the display screen. Under a common initial palette setting, points colored with the attribute 0 appear as black on the display screen. Using the PALETTE statement, you could, for example, change the mapping of attribute 0 from black to white.

Remember that a PALETTE statement executed without any parameters assigns all attributes their default colors.

The following table lists attribute and color ranges for various monitor types and screen modes:

Table 1

SCREEN Color and Attribute Ranges

SCREEN ModeMonitor AttachedAdapterAttribute RangeColor Range
0MonochromeMDPANANA
MonochromeEGA0-150-2
ColorCGANA0-31a
Color/EnhanceddEGA0-31a0-15
1ColorCGANA0-3
Color/EnhanceddEGA0-30-15
2ColorCGANA0-1
Color/EnhanceddEGA0-10-15
7Color/EnhanceddEGA0-150-15
8Color/EnhanceddEGA0-150-15
9EnhanceddEGAb0-30-15
EnhanceddEGAc0-150-63
10MonochromeEGA0-30-8

a Attributes 16-31 refer to blinking versions of colors 0-15
b With 64K of EGA memory
c With greater than 64K of EGA memory
d IBM Enhanced Color Display
NA = Not Applicable
CGA = IBM Color Graphics Adapter
EGA = IBM Enhanced Graphics Adapter
MDPA = IBM Monochrome Display and Printer Adapter

See the SCREEN statement reference page for the list of colors available for various SCREEN mode, monitor, and graphics adapter combinations.

Examples:

PALETTE 0, 2         'Changes all points colored with attribute 0 
                     'to color 2

PALETTE 0,-1         'Does not modify the palette

PALETTE USING A%(0)  'Changes each palette entry. Since the 
                     'array is initialized to zero when it 
                     'is first declared, all attributes are 
                     'now mapped to display color zero. The 
                     'screen will now appear as one single 
                     'color. However, it will still be
                     'possible to execute BASIC statements.

PALETTE              'Sets each palette entry to its appropriate 
                     'initial display color. Actual initial colors 
                     'depend on your screen hardware configuration.

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