Editing Apple GS/OS (section)

===Speed optimization===
The advantage of GS/OS over its predecessor, the ProDOS 16 operating system, is that it was written entirely in 16-bit code for the [[WDC 65C816|65816]] processor used in the II<small>GS</small>, rather than primarily in 8-bit [[MOS Technology 6502|6502]] machine code that does not take advantage of the II<small>GS</small>'s unique features. This in turn allows GS/OS to offer vast speed optimizations (loading time, disk access, screen updates) compared with the previous OS, and provided room to incorporate many features of other Apple operating systems, including [[Apple III]] [[Apple SOS]], the Macintosh [[Classic Mac OS#System Software 5|System 5]], as well as concepts and features that would later appear in future Macintosh System Software releases (e.g. proportional scrollbars, thermometer progress bars).