Additional Information











Before the MultiFinder, introduced in System 7, there was Switcher and then Servant. The largest benefit of the Macintosh 512K and the Macintosh Plus was the additional memory available to users. However, it was still impossible, under Macintosh System Software, to run multiple applications at the same time. While information could be Cut or Copied to the Clipboard, users would have to quit out of MacPaint, for example, before opening MacWrite and pasting in their graphic. Andy Hertzfeld's Switcher allowed Macintosh 512K and Plus users to have multiple applications open at the same time and to switch between these applications, thus making their computer use more productive.



Servant was in development at the same time as Switcher, and the features first developed for Switcher made their way into Servant. However, while Switcher was a little less intuitive in that users had to first select the applications that they wanted to run simultaneously then start switching, Servant allows users to just start opening applications and immediately switch between them. It must be noted, however, that unlike Multi-Mac, Servant does not allow for true multitasking: the foreground application dominates the use of the CPU, and other applications must wait for the user to switch to them before they utilize the CPU. Evidently the only true multitasking support Andy Hertzfeld planned on adding to Servant was support for background tasks such as printing, and possibly support for background modem downloads. Selecting Memory Configuration Information from the Special menu provides the user with a graph of memory usage, as shown below.






Servant tracks the amount of memory used by open applications as well as how much free memory is left available for use. Servant assigns applications a set amount of memory. In addition, Servant allows users to configure the memory allocation for specific applications.



While MacPaint has only 128K assigned to it, Servant allocates 448K for most applications. As shown from the graph, 448K was generally enough for a particular application.


In the screenshot below Servant is the foreground application and Bus'd Out is running the in the background. The Servant menu allows easy switching between applications. A user may also click on a background application to bring it to the foreground. Additionally, the key comination Apple-[ takes the user back to Servant no matter which application is currently in the foreground. Many original Macintosh applications tend to fill the entire screen; Bus'd Out is a good example. For this reason the menu is the easiest way to switch between applications.



With all this memory swapping and hacking at the System level, one might question the stability of applications that were not written with switching in mind. Applications do hang or even crash when running under Servant. Although it does not always work, Apple-Option-Shift-period will force quit a hanging application and leave the others running, if it does not crash the Macintosh. However, I have had applications crash and present the standard Macintosh system error dialog but with a Resume button that actually works, bringing me back to Servant and the other running applications. Typically, however, the Macintosh locks up completely and has to be restarted with the Programmer's Switch.



As Andy Hertzfeld noted in the About window, "Use it with caution, as it is still undergoing testing."



copyright 2002 Josh Burker



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