TURTLE version 1.1e Unit that allows turtle graphics in any BGI mode
Copyright (c) P.Pollet 1991,1992
Portions of SVGA handling copyright (c) 1992 J.P.Hardgrave
Procedures and Functions names (c) Borland Int'l 1987-1992
This unit is hereby donated to the public domain provided:
- the copyright notices are not removed nor modidied.
- proper citation of authors is made upon usage in other packages
- the archive contents is not modified
Please report all problems, bugs, suggested modifications to the author
Dr Patrick L.Pollet email@example.com
Institut National des Sciences AppliquВes
Centre informatique du 1er Cycle Bat 110
20 avenue A.Einstein
69621 Villeurbanne Cedex France
TURTLE DOC This file
DRAGRECT PAS 2411 14.12.92 10:17Demo program Clover dragon
FOREST PAS 3737 14.12.92 10:44Demo program draw a nice forest
NICETREE PAS 3124 14.12.92 10:45Demo program Draw a nice tree
SVGA INI 3192 14.12.92 10:31Include file to use SVGA.BGI
SVGAREG DOC 3122 14.12.92 10:27Registration form for SVGA.BGI
SVGA256 BGI 6335 09.09.92 9:11SVGA.BGI driver (C) J.Hardgrave
TREEREC PAS 1539 14.12.92 9:55Demo program Regular trees
TURTLE PAS 24153 14.12.92 10:30Source code unit Turtle
TURTLEDM PAS 4576 14.12.92 10:05Demo program Play with turtle
VONKOCH PAS 1977 14.12.92 10:29Demo program Von Koch SnowFlake
Why did I wrote that unit ?
Do you remember that little turtle with a pen at the tail
that was the main feature of the Logo language ? A toy to
learn computers to kids ??? Well not so...
For my fellow teachers in C.S., turtle graphics are an
exellent introduction to recursion , with quite attractive
visual effects. Drawing "dragon curves " (Von Koch snowflake,
Peano's curves...) is so natural with this little friendly
Another application is in the representation of 2D shapes
by relative motions of the turtle ; that by a couple (
distance, angle ) from a previous point. This makes the
manipulation of the shape much easier than with the standard
cartesian coordinates representation. A translation just
requires changing the starting point of the drawing ;
rotations can be obtained by changing the turtle heading and
zooming is done by changing the pixel/distance ratio for the
turtle motions. Nearly no trigonometric calculations are
required to transform a shape ...
Borland had introduced turtle graphics with TurboPascal 3.
In the subsequent versions, a compatibilt unit, TURBO3 was
provided but, even with version 6, it can only do turtle
graphics in the old CGA graphic modes !!! Quite desappointing
at the era of SVGA boards....
This unit , TURTLE.PAS make possible the use of a turtle
with any graphic mode supported by the Graph unit. whether it
is a standard graphic mode (EGAVGA,HERC,IBM8570..) or a user
written BGI driver such at the remarkable shareware SVGA
drivers written by .......
To allow a nearly direct recompilation of previous
programs, the entries points are identical , in names and
parameters with the Turbo3 unit interface.
This unit has been tested with all BGI drivers supplied
by Borland Int'l in Turbopascal packages version 5.5 and 6.
User installed BGI drivers were tested only with SVGA.BGI
driver of J.P.Hardgrave.
The source code is self-documented.