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MultiFinder is an extension for the Apple Macintosh's classic Mac OS, introduced on August 11, 1987[1] and included with System Software 5.[2] It added cooperative multitasking of several applications at once – a great improvement over the previous Macintosh systems, which can only run one application at a time. With the advent of System 7, MultiFinder became a standard integrated part of the operating system and remained until the introduction of Mac OS X.


The first Macintosh was released in 1984, and Apple's developers made an early decision that the machine's 128 KB of RAM was so limited that they must abandon the application multitasking functionality that Apple had developed for the Lisa. As the successive Macintosh hardware models were released with much more RAM being the key feature, new programming techniques were developed as workarounds to allow users to run concurrent applications. Desk Accessories became a staple through the lifespan of System 6; and the Switcher would give way to the MultiFinder, which then became directly integrated into System 7.

Desk Accessories[edit]

To allow some degree of freedom and to make good on the GUI's promise of interface consistency, the original Macintosh included Desk Accessories, such as a calculator, that could be run concurrently. However, these were deliberately limited so that they would not use up too much of the available RAM. In fact, they were device drivers which took advantage of the multitasking system designed for hardware peripheral support. As such, their running environment was severely restricted. They could only draw a single window (which by default was given a special round-bordered appearance) and could only run during the vertical blanking interval, which meant that they had to complete processing and redraw themselves every 1/60th second. Since they also couldn't spawn new processes, this made long-running background tasks impossible. Although the system software did little to specifically support them, the popularity of Desk Accessories led many application developers to ensure good cooperative multitasking support even from the early days.


Andy Hertzfeld, one of Apple's original Macintosh software architects, wrote Switcher after seeing John Markoff use a terminate and stay resident program on an IBM PC in October 1984. By the end of the year he had a working prototype, and he soon demonstrated it in public. Both Microsoft and Apple wanted to purchase the utility. Hertzfeld chose the latter offer because Apple offered more money ($100,000 plus royalties) and the company planned to ship Switcher with the Fat Mac. The first official version of Switcher appeared in April 1985.[3]

Switcher works by designating a number of fixed slots in memory into which applications could be loaded. The user can then switch between these applications by clicking a small button on the top of the menu bar. The current application horizontally slides out of view, and the next one slides in. Though awkward, this approach does fit well with the existing system's memory management scheme, and applications need no special programming to work with Switcher.[4] This early work on Switcher led to the development of MultiFinder by Apple system software engineers Erich Ringewald and Phil Goldman.

Microsoft saw Switcher as especially benefiting the company's highly memory-optimized Macintosh applications[3] so the utility was shipped with Excel. Microsoft stated that using multiple applications with Switcher was preferable to a single integrated software application like Lotus Symphony.[5] By 1987, Compute!'s Apple Applications reported that "many Macintosh owners are comfortable only when using more than one application at a time. Switcher and desk accessories are the two most common examples of that philosophy".[6]


MultiFinder, known before its release as "Juggler"[7] was introduced on August 11, 1987[8]. It doesn't provide full multitasking, but simply a way for windows from different applications to coexist by using a cooperative application layering model. When an application is activated, all of its windows are brought forward as a single layer. This approach is necessary for backward compatibility with many of the windowing data structures that were already documented. MultiFinder also provides a way for applications to supply their memory requirements ahead of time, so that MultiFinder can allocate a chunk of RAM to each according to need. This scheme, while functional, turned out to have severe limitations which caused many problems for users.

With the release of System 7, the MultiFinder extension was integrated with the operating system, and it remains so in Mac OS 8 and Mac OS 9. However, the integration into the OS did nothing to fix MultiFinder's inherent idiosyncrasies and disadvantages. These problems were not overcome until the MultiFinder model was abandoned with the move to a modern preemptive multitasking UNIX-based OS in Mac OS X.


  1. ^ "Mac GUI :: MultiFinder Announced". Retrieved October 9, 2017.
  2. ^ Macintosh: System Software Version History, Apple
  3. ^ a b Hertzfeld, Andy. "Switcher".
  4. ^ "Mac GUI :: Switcher hints". Retrieved October 9, 2017.
  5. ^ Pournelle, Jerry (September 1985). "PCs, Peripherals, Programs, and People". BYTE. p. 347. Retrieved March 20, 2016.
  6. ^ "Information On A Card". Compute!'s Apple Applications. December 1987. p. 6. Retrieved August 18, 2014.
  7. ^ "Mac Bulletin". MacWorld. September 1987.
  8. ^ "Mac GUI :: MultiFinder Announced". Retrieved October 9, 2017.