As the original Macintosh was designed without virtual memory or memory protection, it was important to classify code according to when it should be loaded into memory or kept on disk, and how it should be accessed.
The Toolbox consists of a number of 'managers,' software components such as QuickDraw, responsible for drawing onscreen graphics, and the Menu Manager, which maintain data structures describing the menu bar. The Macintosh Toolbox implements many of the high-level features of the Classic Mac OS, including a set of application programming interfaces for software development on the platform.
