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Computing (FOLDOC) dictionary
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computer A home computer made by Commodore with a 6502
CPU, similar in style to the Commodore 64 and CommodoreC16. The VIC-20 was released before the C64, and after the
Commodore PET(?). It was intended to be more of a low-end
home computer than the PET.
The VIC-20 had connectors for game cartridges and a tapedrive (compatible with a C64). It came with five kilobytes
of RAM, but 1.5 KB were used by the system for various
things, like the video display (which had an unusual 22x20
char/line screen layout), and other dynamic aspects of the
operating system (such as it was). The RAM was expandable
with a plug-in cartridge which used the same expansion port as
games. Port expander boxes were available to allow more than
one cartridge to be connected at a time.
RAM cartridges were available in several sizes: 3K, 8K, 16K
and 32K. The internal memory map was re-organised with the
addition of each size cartridge, leading to the situation that
some programs would only work if the right amount of memory
was available. The 32K cartridges were all third-party and
had switches to allow the RAM to be enabled in sections so
that any expansion size could be achieved.
BASIC programs could use at most 24 KB of RAM. Any extra
occupied the location usually used by ROM cartridges
(i.e. games). This allowed people to copy ROM cartridges to
tape and distribute them to their friends, who could load the
tape into the top 8k of their 32k RAM packs.