Commodore Plus 4 - Page 231

Graphics Programming in Machine Language 210
170 Draw a building.
180 Go back for the next building.
190 Save information under first frame.
200 Do the following for ^-coordinates, stepping across the screen by 12.
210 Replace background over the previous frame.
220 Save background under this frame.
230 Get the first frame of jumper.
235 Wait briefly. This is optional. The longer you wait, the slower the
jumper goes, but the smoother the movement seems.
240 Replace background over the previous frame.
250 Save background under this frame.
260 Get the second frame of jumper.
265 Wait briefly as in line 235.
270 Save the coordinate for the next time through.
280 Go back for the next x value.
290 Erase the final frame of the jumper.
300 Write "HIT KEY".
310 Wait for a key. Then return to text mode.
320-340 The coordinates and widths for the six buildings.
Graphics Programming in Machine Language
A great destf of the graphics capacity of your Plus/4 is available from BASIC.
However, there is frequently no substitute for being able to control the graphics
chip directly, especially because it does have capabilities that are not utilized in
the built-in BASIC graphics statements.
The graphics chip operates in one of two modes, either character mode or
bit-map mode. The split screen available from BASIC is not a hardware feature;
it is part of the BASIC language software supplied on ROM inside your
computer.
When operating in character mode, you can choose high-resolution characters,
multicolor characters, or extended color mode. When operating a bit-map mode,
you can choose high resolution (320 by 200) or multicolor (160 by 200). Each of
these possibilities is explored in this section.