Star Tip 7

STAR TIP 7 - sprite mover


by Raffaelle Cecco


from Your Sinclair #24 (December 1987)


[files STARTIP7.*]





Hewson has been very good to use since we started the jolly old Pitstop.


You remember Dominic Robinson's Rainbow Processor program? Well, here's


another Hewson superstar, Raffaelle Cecco, with a great sprite moving


program which, apart from being really nifty, is possible the smallest


chunk of sprite code we've ever seen. And it really couldn't be easier


to use either.





Method





All you have to do is type in the tiny Basic listing ... well, the


single line, actually, and save that off to tape. Then, pass the hex


dump through the Hex Loader, and save that off. Voila! Instant sprites,


just add water. To see a sprite demo, just type:





RANDOMIZE USR 65000





and little YS-shaped sprites will bounce all over the screen. To use the


sprites in a more meaningful way, you have to POKE the following infor-


mation into memory:





POKE 65148 and 65149 with the address of the first sprite (default 65342)


POKE 65129 with X co-ordinate of sprite (0-255)


POKE 65130 with Y co-ordinate of sprite (0-191)


POKE 65131 with sprite number (0-255)


RANDOMIZE USR 65127 to print the sprite on-screen





NOTE: To POKE the address to 65148 and 65149, you need to first convert


the figure into hex (so, for example, 65342 = FF3E), cut it in two (so


you've got FF and 3E hex, or 255 and 62 decimal). Now, the FF bit is


called the 'Hi Byte', and 3E is the 'Lo Byte'. So now you have to POKE


the Lo Byte into 65148 and the Hi Byte into 65149. This way of splitting


up four digit hex numbers is the usual way of POKEing them into memory,


Lo Byte first, Hi Byte second.