System 6 (also referred to as System Software 6) is a graphical user interface-based operating system for Macintosh computers. It was released in 1988 by Apple Computer and was part of the Mac OS line of operating systems. System 6 was shipped with various Macintosh computers until it was succeeded by System 7 in 1991. The boxed version of System 6 cost 49 USD when introduced. System 6 is classed as a monolithic operating system. It featured an improved MultiFinder, which allowed for co-operative multitasking. The last version of System 6 was released in 1991.

A new feature called MacroMaker was included with System 6. When enabled, it allowed users to record mouse and keyboard input as "macros." MacroMaker had a unique user interface, which aimed to look and act like a tape recorder. MacroMaker was criticized for its lack of features when compared to Microsoft's AutoMac III, which was already available commercially. As MacroMaker only recorded the locations of mouse-clicks inside windows and not what was being clicked or exactly when, users soon found that it could not be used to automate more sophisticated programs. The pre-recorded clicks would miss buttons if they had moved or failed to appear upon playback. MacroMaker was not compatible with System 7, which used AppleScript instead.

A system (from Latin systēma, in turn from Greek σύστημα systēma, "whole compounded of several parts or members, system", literary "composition") is a set of interacting or interdependent components forming an integrated whole.

A system is a set of elements (often called 'components' ) and relationships which are different from relationships of the set or its elements to other elements or sets.

Fields that study the general properties of systems include systems theory, cybernetics, dynamical systems, thermodynamics and complex systems. They investigate the abstract properties of systems' matter and organization, looking for concepts and principles that are independent of domain, substance, type, or temporal scale.

Most systems share common characteristics, including:

The term system may also refer to a set of rules that governs structure and/or behavior.

The word system in its meaning here, has a long history which can be traced back to Plato (Philebus), Aristotle (Politics) and Euclid (Elements). It had meant "total", "crowd" or "union" in even more ancient times, as it derives from the verb sunìstemi, uniting, putting together.