Scroll colour Bill Longley, Colchester, Essex. Most ZX-81 users will have a selection of machine-code routines for inverting the display and scrolling in different directions. Unhappily for those who upgrade to a Spectrum, these are not compatible with the high-resolution display file. But many of the principles remain the same and here are three typical subroutines for the Spectrum. The first two are the up-and-down scrolling routines, but here they scroll colour while the text remains still. The third is an ordinary screen invert routine. It will exchange the ink dots for paper dots, and vice versa. This probably only makes sense to Spectrum users. Three separate REMs are used to store the routines, so one routine can be used on its own. If you make sure each REM has 32 characters - remember a colour control code is two - then each routine starts at an address which is 38 greater than the last; so the first starts at 23760, the next at 23798, the third at 23836 and so on. One last point: it makes good sense to save each routine on tape - with different line numbers - and MERGE them into your program as you need them. [In fact, all three routines are relocatable, so you don't have to load them into REMs at all. Loading them into any other available part of memory should work fine.]