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System 7 refers to the Mac OS that superseded the earlier versions of the Macintosh System Software before the term "Mac OS" came into official use. "System 7" is used to apply to all the 7.x versions. The codename for System 7.0 was "Big Bang", which reflects the considerable changes that came with it.
System 7.0 was released for the Apple Macintosh on May 13, 1991. It offered a number of system enhancements that were either previously not available, or were optional extensions to the operating system.
Compared with System 6, System 7 offered:
- 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 earier system versions.
- 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.
- 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.
- 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.
- System 7 started to pave the way to move to a full 32-bit address space, 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.
There were also a large number of architectural changes to make the OS more coherent and stable. Apple boasted on its release that System 7 was "rock solid", and while it was a great improvement over the earlier systems, the claim was rather hyperbolic. Many also felt that performance suffered as a result of upgrading from System 6 to System 7, though new hardware soon made up for the speed loss.
System 7.0 was adopted quite rapidly by Mac users, and quickly became the base requirements for new software. Until the advent of OS X, System 7 was by far the largest shake-up and revamp of the Mac OS since its inception. Unlike the transition to OS X, the System 7 transition from System 6 was smooth, largely transparent (meaning new features were implemented elegantly, and the look and feel was mostly unchanged), and widely adopted as the standard Macintosh operating system. Mac OS 8 and Mac OS 9 were relatively minor upgrades from System 7.x, compared to the changes from 6.x to 7.0.
The coding group within Apple responsible for System 7 were known as the "blue meanies" after the blue slips of paper on which were written the features that could be implemented in a relatively short time. In comparison, the pink-slipped features were handled by the Pink group, later becoming the ill-fated Taligent project. Despite the idea of System 7 being the "quick win", it was still delivered several years late.
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