The Macintosh, like most desktop computer systems today, is a raster-based
image system -- not a vector-based system. Vector data can be entered, but
needs to be converted to a line drawing system based on cartesian coordinates
for displaying on the screen. Specifically, for the Macintosh, this means that
the vector data needs to be converted into QuickDraw data and then drawn with
QuickDraw routines.
If you want to create your own CAD program, you need to understand both the
vector system and the QuickDraw system, as well as do the conversion between
the two methods. Your implementation of your vector system will determine the
number of vectors handled.
On the other hand, if you want to use a commercial application, the vector
limits are a specification of that commercial application. The application
also converts the vector information into QuickDraw information for screen
display. However, some commercial developers have bypassed QuickDraw and
written directly to the Macintosh hardware. In these instances, the
applications do not benefit from the accelerated QuickDraw of the new Display
Card 8/24 GC. These applications also have a higher probability of breaking on
newer models of the Macintosh.
The speed at which vectors are handled (as vectors) depends on the
application's implementation and the speed of the CPU on which that application
is run. The faster the CPU, the faster the application. The speed of the
conversion from vectors to QuickDraw is also application- and CPU
speed-dependent. The speed with which QuickDraw is handled is a function of
the Display Card 8/24 GC and the CPU speed.
Expanding the memory of the Display Card 8/24 GC allows a larger off-screen
bitmapped image to be stored directly on the video card. This speeds up the
movement of images larger than the screen as they move on to and off of the
screen. The expanded memory acts a holding space for the off-screen bitmapped
image.