Turbo Prolog

8 Tutorial VI:
Graphics and Sound
Apart from windows, the other way to brighten up your programs is to use graphics
and sound. Turbo Prolog offers a choice of point- and line-based graphics or a full set of
Turtle Graphics commands. Complex shapes are easy to draw with Turtle Graphicsall
you have to do is guide a little pen-carrying turtle around the screen. This chapter
describes these facilities in detail, gives some attractive example programs and concludes
with two applications of the sound standard predicate, one of which turns your
computer into a piano!
TURBO PROLOG'S GRAPHICS
Before using Turbo Prolog's graphics commands, you must set up the screen in an
appropriate way using the standard predicate graphics. When you've finished with
graphics, the standard predicate text can be used to clear the screen and return to text
mode.
The graphics predicate takes the form
graphics(ModeParam,Palette,Background)
and initializes the screen in medium, high or extra-high resolution graphics. The possible
values for ModeParam and the resulting screen formats are shown in Table 8-1. The
standard IBM Color/Graphics Adapter supports modes I and 2: and modes 3,4, and 5
are supported by the Enhanced Graphics Adapter. In all cases, graphics clears the
screen and positions the cursor at the upper left corner.
In mode I four colors can be used (colors 0, 1,2, and 3), as shown in Table 8-2. Color °
is the current background color. Colors are determined by one of two palettes,
selected according to whether Palette is bound to ° or I. Modes 3 and 4 offer sixteen
colors, and mode 5 offers 3.
Background (also an integer value) selects one of the background colors shown in Table
8-3.
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