System 6 is a graphical user interface-based operating system for Macintosh computers. It was released in 1988 by Apple Computer, Inc. and is part of the classic Mac OS series of operating systems. System 6 was included with all new Macintosh computers until it was succeeded by System 7 in 1991. The boxed version of System 6 cost $49 when introduced. System 6 is classed as a monolithic operating system. It features an improved MultiFinder, which allows for co-operative multitasking.
Main features
MacroMaker
MacroMaker is a utility introduced in System 6. When enabled, it allows users to record mouse and keyboard input as macros. MacroMaker has a unique user interface, which aims 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 records the locations of mouse-clicks inside windows and not what is being clicked or exactly when, it can not be used to automate more sophisticated programs. The pre-recorded clicks miss buttons if they had moved or failed to appear upon playback. Another limitation is that it records the start and end locations of mouse movements but not the precise path of the movements, and its macros do not handle situations that require the macro to wait for a period of time before or after an action. MacroMaker is not compatible with System 7, in which the successive AppleScript was introduced.
Multitasking
Cooperative multitasking made its Macintosh debut in March 1985 with a program called Switcher by Andy Hertzfeld, which allows the user to launch multiple applications and switch between them. Many programs and features do not function correctly with Switcher, and it does not share the screen between applications simultaneously. It is not included with the operating system, but was available from Apple as a separate purchase. Both System 5 and System 6 have a feature called MultiFinder instead, which is much more mature and widely used in System 6. MultiFinder can be enabled or disabled, with a reboot. If disabled, the Finder quits when the user launches another application, thus freeing RAM for it. If enabled, the system behaves as in the currently familiar multitasking tradition, with the desktop and windows of other applications in the screen's background.
System 6's Apple menu cannot be used to launch applications. The current application icon in the upper right-hand corner of the menu bar cycles between open applications; it is not a menu. System 6 supports 24 bits of addressable RAM, which allows a maximum of 8 megabytes of RAM with no provision for virtual memory. These limitations were fixed in System 7. The version of the HFS file system in System 6 also has a volume size limit; it supports up to 2 gigabytes and 65,536 files on a volume. System 7.5 increases the limit to 4 GB. The Trash empties when the Finder terminates. If MultiFinder is not running, this occurs as soon as an application launches. Icons on the desktop in System 6 are not organized into a single folder, as in later operating systems. Instead, the system records whether each file is on the desktop or not. This is inefficient and confusing, as the user cannot browse to the desktop in applications besides the Finder, even within the standard Open and Save Asdialog boxes. Furthermore, these dialogs are primitive, mostly unchanged since 1984. The lack of aliases, shortcuts to files, is another limitation of file management on System 6. Custom file and folder icons are not supported. These problems were all remedied in System 7. A maximum of 15 desk accessories may be installed at one time, including the Chooser, Scrapbook, and Control Panel. System 6 uses the Control Panel desk accessory to access all the installed control panels, which imposes severe user interface limitations. Desk Accessories cannot be installed or removed within the Finder; this requires the Font/DA Mover utility. System 7 also fixed this. Control panels, however, are contained in separate files. Few methods exist for interface personalization. The Finder allows each icon to be assigned a color, but the desktop background is limited to an 8x8 pixel color tiled pattern, and standard window frames are all black and white. However, many "INIT" extension files exist to add color and customization. System 7 allows the user to change the color and various other aspects of the user interface. By 1989, the System 6 user interface was in need of a change. In comparison to the NeXTSTEP operating system of the time, System 6 does not make use of sound, and its user interface presented several limitations in file management and the way windows are displayed.
Reception
The initial releases of System 6 are unstable; many third party software developers did not receive copies before its release, resulting in widespread compatibility problems. The contemporary versions of many common software programs such as Microsoft Excel, Microsoft Works and 4th Dimension are not fully compatible with System 6. There are also software bugs in the Color Manager, Script Manager, and Sound Manager extension files. Apple announced that 66 bugs were fixed when the 6.0.1 update was released in September 1988. However, a major bug involving text spacing of screen fonts was found in 6.0.1 after distribution began. This led to the quick release of 6.0.2, which solves this problem. Some customers waited longer until moving to System 6 because of the poor reputation already gained.
Compatibility
System 6 was officially supported by Apple for many different machines, some of which were shipped with System 6. Some unsupported Macintosh computers can run System 6 with limitations.
