System 7

System 7 (whose codename being "Big Bang" reflects the considerable changes that came with the OS) refers to the Mac OS that superseded "The System" or "System 6" before "Mac OS" came into official use. The name reflects the version number of the OS—7.0, but the term is also used to apply to all the 7.x versions, both those labeled "System" and those labeled "Mac OS."

System 7.0 was released for the Apple Macintosh on May 13, 1991. It offered a number of system enhancements that had previously been absent, or only available as optional extensions to the operating system.

New Features

File:Apple System 7 Macintosh Basics Demo

• Built-in co-operative multitasking. Previously this function was available through the MultiFinder in System 6, or not available at all. Because more than one application could run at a time, Desk Accessories were deprecated, System 7 treating them no different from other applications.

• The Trash was now a real folder instead of the special status it previously had. This allowed items to be put in the trash on different volumes, each one having its own Trash.

• Personal File Sharing. Along with various user interface improvements for AppleTalk setup, System 7 also included a basic file sharing server allowing any machine to publish folders to the AppleTalk network.

• The Control Panel became the Control Panels — they became individual "windows of options" accessible from the Control Panels folder in the Finder, instead of being accessible using the previous Control Panel Desk Accessory in earlier system versions.

• In a similar fashion, system "extensions" were also improved by placing them in their own folder (rather than the System folder's root), and holding down the Shift key during boot-up would disable them. The line between extensions and control panels was blurred, extensions basically being GUI-less control panels.

• Aliases: small files that "pointed to" other files on the system. This was added to help the user navigate the increasingly larger disks that were starting to appear.
• The Apple menu (previously home only to Desk Accessories pulled from DRVR resources in the System file) now listed the contents of a folder, including aliases. Desk Accessories had originally been intended to provide a form of multitasking and were no longer necessary now that multitasking was always enabled. The desk accessory technology was deprecated, with System 7 treating them largely the same as other applications.

• Application menu. A list of running applications, formerly at the bottom of the Apple menu under MultiFinder, was moved to its own menu on the right, along with Hide and Unhide functionality.

• AppleScript. This was an entire architecture for making scriptable applications. While fairly complex for programmers to implement, this feature was powerful and popular with users, and is still available to this day as part of Mac OS X.

• 32-bit QuickDraw, supporting so-called "true color" imaging was included as standard—it was previously available as a system extension.

• Publish and Subscribe. This feature permitted data "published" by one application to be imported ("subscribed") by another, and the data could be updated dynamically. The feature was not terribly popular with programmers, who found the API unwieldy, and users didn't seem all that interested either. Relatively few applications ended up adopting it.

• Balloon Help provided on-screen tooltips. A Help menu was added to the menu bar to control it.

• TrueType, a new outline font technology developed by Apple.

• A new full-color user interface was included which gave a neat color appearance on color machines but which gracefully dropped back to the standard black and white interface on machines not supporting color.

• A new Sound Manager API which replaced the older ad-hoc APIs that did not abstract the hardware to any great degree. (This was also included with System 6.0.8.)

• System 7 started to pave the way to move to a full 32-bit addressing system, from the previous 24-bit address space, which limited memory to a maximum of 8MB. This process involved making all of the routines in OS code use the full 32-bits of a pointer as an address - prior systems used the upper bits as flags. This change was known as being "32-bit clean". While System 7 itself was 32-bit clean, many existing machines and thousands of applications were not, so it was some time before the process was completed. Additionally, "32-bit dirty" (i.e. non-"32-bit clean") Macs no longer ran any version of the system software as of version 7.6.