Q. I hve a few Vic 20 questions. When you add 8K or more memory, where does the colour, screen and sound memory move to? Using a motherboard, can a Super Expander cartridge be used with 16K memory? Will the Super Expander work with the programmer's aid cartridge?

Finally, is the Vic to be replaced by the Commodore 16, and when will software and peripherals follow?

Stephen Pascoe
Lancing, Sussex

A. The moving memory map is perhaps the biggest peculiarity of the Vic. Essentially there are two configurations - unexpanded and expanded. However, for memory-mapping purposes, adding a 3K expansion still gives you an unexpanded Bic. With us so far? Good.

With up to 8K of RAM (the original 5K plus 3K expansion) everything stays in the same place - colour and screen memory and so on. By the way, the sound registers never move, nor do the graphics registers.

Adding 3K fills the empty memory area from 1024 to 4096. Screen memory stays at 7680 with colour at 38400.

When you add 8K or more, screen memory moves from the end of Basic memory to the beginning and colour memory moves down by 0.5K. So screen memory goes to 4096 and colour to 37888.

You can use the Super Expander commands with 16K memory expansion but you won't be able to use the 3K memory in the expander for Basic. You can only get to it in machine code or by PEEKing and POKEing data.

You can't use two program cartridges at a time since they use the same dedicated area in the high memory.

On the question of the new Commodore 16, the company has said that it will support the Vic as long as demand continues but it seems likely that third party companies will concentrate on the new machines and the C64, so long term support for the Vic looks shaky.