QuickDraw was grounded in the Apple Lisa's LisaGraf of the early 1980s and was designed to fit well with the Pascal-based interfaces and development environments of the early Apple systems. In addition, QuickDraw was a raster graphics system, which defines the pixel as its basic unit of graphical information. This is in contrast to vector graphics systems, where graphics primitives are defined in mathematical terms and rasterized as required to the display resolution. A raster system requires much less processing power however, and was the prevailing paradigm at the time that QuickDraw was developed.