Screen Saver

SCREEN SAVER


by Richard Swann





Back (back! Back!) in full effect, Dicky's second contribution of the


month is none other than a screen saver utility as found on, quoth


Dicky, "posh computers". Just an interjection of mild interest at this


point - the equivalent of both Richard's programs this month can be


found already built into the ROM of that "posh computer", the SAM


Coupe, and it's good to see Dicky acknowledging the SAM's superiority


at last!





For those not in the know, such a prog is used to blank the screen out


after 'n' minutes, so as to save the TV's phosphor from sustaining a


permanent scar due to displaying a static image for too long. To


actually use the thing, you first need to work out after how many


frames you want the screen to blank out. The value can be anything up


to 65535, which works out at about twenty-two minutes, and just to


give you a rough working guide, one frame lasts one fiftieth of a


second. Using n as the number of frames, POKE 64847, n-INT(n/256)*256:


POKE 64848,INT(n/256): RANDOMIZE USR 64768 and you're away. Two words


of warning, though - firstly, don't use interrupts, and secondly,


leave all RAM above 64768 free for the routine to use.