The Logo language, which is popular among young computer users, made the concept of turtle graphics famous. Imagine a mechanical turtle that walks around the room under the control of a Java program. The turtle holds a pen in one of two positions, up or down. While the pen is down, the turtle traces out shapes as it moves; while the pen is up, the turtle moves about freely without writing anything. In this problem you will simulate the operation of the turtle and create a computerized sketchpad as well.
Use a 20-by-20 array floor which is initialized to zeros. Read commands from an array that contains them. Keep track of the current position of the turtle at all times and whether the pen is currently up or down. Assume that the turtle always starts at position 0,0 of the floor with its pen up. The set of turtle commands your program must process are as follows:
| Command | Meaning |
|---|---|
| 1 | Pen up |
| 2 | Pen down |
| 3 | Turn right |
| 4 | Turn left |
| 5,10 | Move forward 10 spaces (or a number other than 10) |
| 6 | Print the 20-by-20 array |
| 9 | End of data (sentinel) |
Suppose that the turtle is somewhere near the center of the floor. The following "program" would draw and print a 12-by 12-square leaving the pen in the up position:
2
5,12
3
5,12
3
5,12
3
5,12
1
6
9
As the turtle moves with the pen down, set the appropriate elements of array floor to 1s. When the 6 command (print) is given, wherever there is a 1 in the array, print an asterisk. Wherever there is a zero, print a blank. Write a program to implement the turtle graphics capabilities discussed here. Write several turtle graphics programs to draw interesting shapes. Add other commands to increase the power of you turtle graphics language.