Forwards and backwards

The and keys are used to tell the PIP symbol to move forwards or backwards. After you press these you must press some numbers to tell it how far to go. 20 is about the length of the symbol.

Try this little program:-

The text for the program will appear above the keyboard and the symbol will move forwards about it's own length and then sing.

You can make the program longer by pressing:-

The simulator will do the old commands and then the new ones. It will move forwards about its own length and then backwards the same length. As it runs, the program step that it is executing is highlighted and the current position of the PIP symbol is shown at the top right of the screen.

The numbers you give for distances can be as much as 999. If you try to enter the number 0, you will get an error message.

If the PIP symbol reaches the edge of the graphics area, it will stop and you will get a "crashed!" error message.


The and keys tell the PIP symbol to turn left or right (anticlockwise or clockwise). After you press these you must enter a number to tell it how many degrees to turn. 360 degrees make a complete circle.

You can make the PIP symbol go anywhere in the graphics area using the turn, forwards and backwards arrows. This program will make it follow a square path:-

You will sometimes want to move the PIP symbol back to the centre. The button on the right-hand side of the screen moves the PIP symbol back to the centre. It does nothing else.

Date Last Modified: 10/9/01