System

1. When referring to an Apple Macintosh, System is the computer's operating system, or MacOS. System is commonly followed by a number, for example: System 7.
   
   Additional information about Macintosh operating systems can be found on our MacOS help page. 
   
   
2. When referring to computer hardware, system is often used to distinguish the complete computer as a whole.
3. When referring to software, system is sometimes used to abbreviate operating system.

Also see: Macintosh, Operating System definitions