From Wikipedia, April 25, 2007
System 7 (codenamed Big Bang and sometimes called Mac OS 7) is a version of the Mac OS, the operating system of the Macintosh computer, introduced in May 13, 1991. It succeeded System 6, and was the main Mac operating system until it was succeeded by Mac OS 8 in 1997. Features added with the System 7 release included cooperative multitasking, virtual memory, personal file sharing, an improved user interface look, QuickTime, and QuickDraw 3D. It is still used by a small number of Macintosh users who own legacy Apple hardware of that era.
Note that "System 7" is often used as a generic term to refer to all 7.x versions. With the release of version 7.6 in 1997, Apple officially renamed the operating system Mac OS. System 7 was developed for the Motorola 68k processor, but was ported to the PowerPC, after Apple adopted the new processor.
Compared with System Software 6, System 7 offered:
Built-in co-operative multitasking. In System Software 6, this function was optional through the MultiFinder.
Trash was now a formal directory, allowing items to be preserved between reboots instead of being purged.
Personal File Sharing. Along with various UI improvements for AppleTalk setup, System 7 also included a basic file sharing server allowing any machine to publish folders to the AppleTalk network.
Aliases. An alias is a small file that represents another object in the file system. A typical alias is small, between 1 and 5 KB. It acts as a redirect to any object in the file system, such as a document, an application, a folder, a hard disk, a network share or removable medium or a printer. When double-clicked, the computer will act the same way as if the original file had been double-clicked. Likewise, choosing an alias file from within an "Open" dialog box would open the original file. (Unlike the path-based approach of Microsoft Windows 95, aliases also store a reference to the file's catalog entry, so they continue work even if the file is moved or renamed. Aliases can be best described as a fusion of a hard link and a symbolic link on Unix-based systems, including Mac OS X.)
"System Extensions" (small pieces of INIT code that extended the system's functionality) were improved by relocating them to their own subfolder (rather than in the System Folder itself as on earlier versions), and by allowing the user to hold down the Shift key during bootup to disable them. Later versions of System 7 offered a feature called "Extensions Manager" which simplified the process of enabling/disabling individual extensions. Extensions were often a source of instability and these changes made them more manageable and assisted trouble-shooting.
The Control Panel Desk Accessory became the Control Panels folder (found in the System Folder, and accessible to the user from an alias in the Apple menu). The control panels themselves became separate files, stored within this directory.
The Apple menu (previously home only to Desk Accessories pulled from "DRVR" resources in the System file) now listed the contents of a folder ("Apple Menu Items"), including aliases. Desk Accessories had originally been intended to provide a form of multitasking and were no longer necessary now that real multitasking was always enabled. The Desk Accessory technology was deprecated, with System 7 treating them largely the same as other applications. Desk Accessories now ran in their process rather than borrowing that of a host application.
The Application menu, a list of running applications formerly at the bottom of the Apple menu under MultiFinder, became its own menu on the right. In addition, Hide/Show functionality was introduced, allowing the user to hide applications from view while still keeping them running.
Balloon Help, a widget-identification system similar to tooltips.
AppleScript, a scripting language for automating tasks. While fairly complex for application programmers to implement support for it, this feature was powerful and popular with users, and a version of it is still available to this day as part of Mac OS X.
AppleEvents. Supporting AppleScript was a new model for "high-level" events to be sent into applications, along with support to allow this to take place over the AppleTalk network.
32-bit QuickDraw, supporting so-called "true color" imaging, was included as standard; it was previously available as a system extension. QuickDraw was used in Mac OS for fast on-screen drawing.
Publish and Subscribe. This feature permitted data "published" by one application to be imported ("subscribed to") by another, and the data could be updated dynamically. Programmers complained that the API was unwieldy, and relatively few applications ended up adopting it.
TrueType outline fonts. Up to this point, all fonts on the Macintosh were bitmapped, or a set of bitmapped screen fonts paired with outline PostScript printer fonts; TrueType for the first time offered a single font format that looked great at any size on screen and on paper. This technology was recognized as being so important that a TrueType extension for System 6 was also released, along with an updated Font/DA Mover capable of installing these new kinds of fonts into the System 6 System file.
A new full-color user interface. Although this feature made for a visually-appealing interface, it was optional. On machines not capable of displaying color, or those with their display preferences set to monochrome, the interface defaulted back to the black-and-white look of previous versions. Only some widgets were colorized — scrollbars, for instance, had a new look, but buttons remained in black and white.
A new Sound Manager API, version 3.0, replaced the older ad hoc APIs. The new APIs featured significantly improved hardware abstraction, as well as higher-quality playback. Although technically not a new feature for System 7 (these features were available for System Software 6.0.7), Sound Manager 3.0 was the first widespread implementation of this technology to make it to most Mac users.
System 7 paved the way for a full 32-bit address space, from the previous 24-bit address space. 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. To ease the transition, the "Memory" control panel contained a switch to disable this feature, allowing for compatibility with older applications.
System 7 was the first version of the Mac OS that required a hard drive because a full installation was too large to fit on a 1.44 MB floppy disk. It did not come bundled with major software packages itself, but newly purchased Macintosh computers often included bundled software such as Millie's Math House, Power Pete, HyperCard and ClarisWorks. PowerPC Macintoshes included Graphing Calculator. System 7 also included networking and file sharing software in the form of system extensions and control panels.
The basic utilities installed by default with System 7 included SimpleText for basic text editing tasks and reading Readme documents. Also available on the additional "Disk Tools" floppy disk are Disk First Aid for disk repair and Apple HD SC Setup for initializing and partitioning disks.
Later versions of System 7, specifically System 7.5 and 7.6, came with a dedicated "Utilities" folder and "Apple Extras" folder including: AppleScript, Disk Copy, QuickDraw GX Extras and QuickTime Movie Player. More optional extras and utilities could be manually installed from the System Software disc.
When Apple transitioned to the PowerPC processor, 68k applications were emulated on the new processor, while fat binaries allowed software to run natively on both 68k and PowerPC systems. This was a migration process similar to the current distrtibution of Universal Binaries for the PowerPC- to Intel -Mac transition which began in 2006. See also: Mac 68K emulator.
With support for color displays, shareware developers also started to develop more realistic arcade games for the Macintosh such as Pac-Man clones and later 3D games such as Tomb Raider and Marathon. Although 3D rendering technology was not available as a standard system feature until the introduction of QuickDraw 3D, many of the most innovative titles of the time were produced for System 7, using their own 3D engines.
System 7 Pro, System 7.5 and up shipped with PC Exchange, previously a separate product, which allowed MS-DOS and Microsoft Windows-formatted floppy disks to be read. Before System 7 Pro, Apple File Exchange was used.
At the time of its release, many users noticed that performance suffered as a result of upgrading from System Software 6 to System 7, though newer hardware soon made up for the speed differential. Another problem was System 7's large "memory footprint": System Software 6 could boot the system from a single floppy disk and took up about 600 KB of RAM, whereas System 7 used well over a megabyte, and could no longer be usefully run from floppy-only machines. (Versions up to 7.5 could boot from a floppy, but there would be no room for other applications, although it was possible to access an AFP server on an AppleTalk network.) It was some time before the average Mac shipped with enough RAM built in for System 7 to be truly comfortable. Offsetting this was the inclusion of a hard disk as standard in most Mac models; only the long-lived Mac Plus and certain models of the Macintosh SE did not ship with one.
System 7.0 was adopted quite rapidly by Mac users, and quickly became one of the base requirements for new software.
The engineering group within Apple responsible for System 7 came to be known as the "Blue Meanies", named after the blue index cards on which were written the features that could be implemented in a relatively short time. In comparison, the pink index card features were handled by the Pink group, later becoming the ill-fated Taligent project.
Soon after the initial release of System 7, the 7.0.1 minor update was released in October 1991. A patch called "System 7 Tune-Up" also followed, which fixed the "disappearing files" bug in which the system would lose files. In August 1992, the 7.1 update was released which introduced the Fonts folder, allowing users to organize their fonts in the Finder, replacing the Font/DA Mover application used in System Software 6.
The first major upgrade was System 7.1.1, also known as System 7 Pro. This release was a bundle of 7.1 with AppleScript tools, QuickTime and Apple Open Collaboration Environment (AOCE). While System 7 had some trouble running in slightly older machines due to memory footprint, System 7 Pro barely fit into any Macintosh computers at the time. It was most commonly used for its minor bug fixes rather than its new functionality.
Apple joined the AIM alliance (Apple, IBM and Motorola) shortly after the release of System 7 in 1991, and started work on PowerPC-based machines that later became the Power Macintosh family. Support for these machines resulted in System 7.1.2.
System 7.1.2 was never offered for retail sale; it shipped with the first batches of the PowerPC Macs. Later shipments shipped with System 7.5 instead.
The next major release was System 7.5, (codenamed Capone -- a reference to the gangster who put fear in Chicago, which was also the code name for Microsoft's Windows 95) which included bug fixes from previous updates and added several new features including:
- an updated startup screen featuring a progress bar
- introduction of the nanokernel, which managed low-level hardware and system softwareinteractions such as interrupt handling.
- a new interactive help system called Apple Guide
- a clock in the menu bar (based on the free "SuperClock" control panel by Steve Christensen)
- an Apple menu item called Stickies (formerly a third-party application called "PasteIt Notes") which provided virtual Post-It Notes
- WindowShade (another former shareware control panel which provided the ability to condense a window down to its title bar)
- the Control Strip (a fast way to change the system volume, control the playback of audio CDs, manage file sharing and printers and change the monitor resolution and color depth)
- the Extensions Manager (enabling the user to turn extensions and control panels on and off; also based on a formerly third-party control panel)
- PowerTalk, the predecessor to the Keychain system and also a system-level email handling service
- the Launcher, a special Finder window containing shortcut buttons for frequently-used programs (in a manner somewhat akin to the Mac OS X Dock)
- a hierarchal Apple menu (folders within the Apple Menu Items folder would expand into submenus showing their contents)
- system-wide drag & drop for text and other data (selections could be simply dragged with the mouse and dropped to their new destination, bypassing the clipboard)
- a scriptable Finder
- QuickDraw GX, a 2-D graphics rendering and geometry engine
- support for OpenDoc
System 7.5.1 was primarily a bug fix on 7.5, but also introduced a new "Mac OS" startup screen in preparation for Mac clones.
System 7.5.2, released only for the first PCI-based Power Macs, was notable for introducing Apple's new networking architecture, Open Transport and also for being the most unstable version of Mac OS in recent memory.
System 7.5.3, a major bug-fix update that also included Open Transport for other PowerPC-based machines as well as some 68k-based machines. 7.5.3 also made several improvements to the 68k emulator, and added translucent dragging support to the Drag Manager.
System 7.5.4 was pulled due to a mistake at Apple, where some components were not included in the installer, and replaced with System 7.5.5.
In addition to this, Open Transport was updated separately twice.
Mac OS 7.6 (codenamed Harmony) was the last major update, released in 1997. With 7.6, the operating system was officially called "Mac OS" instead of "System". Mac OS 7.6 introduced several features that were also included in Mac OS 8, including a revamped Extensions Manager, more native PowerPC code for Power Macs, more bundled Internet tools and utilities, and an overall more-stable Finder. In this version, the PowerTalk feature added in 7.5 was removed due to poor application support.
The minor update to Mac OS 7.6.1 finally ported the 68k exception handling routines to PowerPC, turning most type 11 errors into more meaningful errors (type 1, 2 or 3, usually).
Through this period Apple had been attempting to release a completely new "modern" operating system, named Copland. When the Copland project was abandoned in 1996, Apple announced plans to release an OS update every six months until Rhapsody (which would later evolve into Mac OS X) shipped. Two more releases were shipped, now officially branded as the "Mac OS" — Mac OS 7.6 and the minor bug fix 7.6.1. Future versions were released as Mac OS 8–8.6 and Mac OS 9–9.2.2.
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