4
The
VIC
20
User
Guide
configuration. Instructions for connecting the printer and disk drive to the
VIC
20
are provided later in this chapter.
Video
Port
The VIC
20
produces the sound and pictures displayed on your
television by combining them into a signal called composite video. This
signal
is
sent out through the video port.
A video monitor (a television without a tuner)
is
able to convert the
composite video directly into pictures and sound. A television, however,
must be tuned to a particular channel. That signal
is
produced and
combined with the composite video by the
RF
(radio frequency) modulator
(the small black box in Figure
1-1).
When you use the VIC
20
you can select either channel 3
or
channel 4
by flipping the channel switch on the side of the modulator.
Expansion
Interface
The expansion interface gives you access to the computer's memory
lines. Through it you may increase the memory size of your VIC
20
to as
much as 32K (more than 32,000 bytes).
NOTE:
Increasing the memory size may cause the computer's memory
to be reconfigured. This will cause the screen display information and some
parts of user memory to
be
moved to other locations in memory. Generally,
this will cause no noticeable changes.
In
some cases, however, it will cause
program run failures. Look
at
the memory map in Appendix B for specific
information on memory expansion and reconfiguration.
Video Display
When you first power up the VIC
20
it displays
23
rows with
22
characters per row. The computer generates these characters by lighting the
appropriate pattern
of
dots within an 8 X 8 matrix. This
is
illustrated in
Figure
1-3.
The VIC 20's character set
is
quite extensive, containing
256
letters, numbers, and symbols.
It
is
also possible to program custom
characters for special applications. This
will
be
discussed in Chapter
6.
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