System 7 (Mac OS)

System 7 is a version of Mac OS, the operating system of Macintosh personal computers introduced on May 13, 1991, and was the main operating system of the Mac until it was replaced by Mac OS 8 in 1997. Features added to System 7 included Cooperative Multitasking, virtual memory, personal file sharing, QuickTime, QuickDraw 3D and an improved graphical interface. Nowadays it is still used by a small number of Macintosh users that use computers based on Motorola 68000 family microprocessors.

Note that "System 7" is used as a generic term to refer to all its versions. With the release of version 7.6 in 1997, Apple officially changed the name of the operating system to Mac OS, a name that first appeared in System 7.5.1. System 7 was developed for Motorola 68k processors but was ported to PowerPC, when Apple adopted the use of the new processor.

Development

Shortly before the release of System 6 in March 1988, the Cupertinos held a visiting meeting to discuss plans for the further development of the "apple" OS. The tasks were written on cards: those that seemed fairly simple to implement in the short term (such as adding color to the user interface) were written on blue cards, and long-term goals (like full multitasking) were written on pink cards, and the most difficult ones (as an object-oriented file system) on red. The implementation of the tasks outlined in blue and pink cards was supposed to take place simultaneously on the first two projects code-named "Pink" and "Blue", respectively (including the project "Taligent ru en"). Through the efforts of the "blue" team, who called themselves "Blue Meanies" in honor of the characters of the cartoon "Yellow Submarine", Apple intended to release an updated version of the existing OS for "Macs" in 1990—1991, and the team of "pink" was to develop a completely new OS by about 1993.

Switching to PowerPC

By the beginning of the 1990s, it became obvious that the Motorola 68k processors were obsolete, and the Macs needed a switch to a fundamentally new architecture. ARM seemed an interesting solution, but at that time the processor performance on this architecture was low. Processors from Intel were quite expensive. Ultimately, in 1991, the AIM alliance was formed, which included Apple, IBM and Motorola, which resulted in the emergence of PowerPC micro architecture. System 7 began to support PowerPC, starting with version 7.1.2. Due to the lack of software, the built-in 68k emulator loaded without starting FPU and PMMU when starting the OS, thus the ability to install A/UX has been closed. To simplify the development of new software for PowerPC, a special nanocore was written - smaller in size than the microkernel used. It was launched with the highest priority, acted as a layer of hardware abstractions and provided low-level interfaces for handling interrupts, exceptions, and memory management. Only OS system services and the debugger could access it directly.

It is worth noting that the first versions of the classic Mac OS for PowerPC contained quite a bit of platform-specific code. Most of the applications, drivers that existed at that time, and most of the Toolbox and the OS code itself were run in emulation mode only. It was assumed that a nanonuclear architecture would help to simplify porting and software development for PowerPC. Similarly, Apple made the switch from PowerPC to Intel processors in 2006.

Features

Comparing to System 6, System 7 offered

• Native cooperative multitasking. In System 6, this feature is optional through the MultiFinder.
• The trash is now a formal directory, so the files are not deleted when you restart the computer.
• Easy to share files between users in AppleTalk network, provided a more stable and common communication for other computers.
• Alias - An alias is a small file that represents another object in the file system. The typical alias is small, between 1 and 5 KB. It acts as a redirector to another object such as a document, an executable, a directory, a hard disk, a file or network volume, a removable drive or a printer. By double clicking on it, the system behaves as if it had been done in the original file. In addition, if an alias file is chosen from an opening dialog box, the original file is opened. Unlike the path-based mechanism of Windows 95, the alias also stores a reference to the file entry in the system catalog, so it continues to work if the file is moved or renamed. An alias can be described as a merger between a hard link and a symbolic link of Unix- like operating systems (such as Mac OS X).
• The System Extensions (small INIT code files that extend the functionality of the system) were improved by replacing them in their own directory, instead of being at the root of the System Folder (name of the operating system folder on Macs) as in versions previous. The user is also allowed to disable them by holding down the "Shift" key during startup. Later versions of System 7 incorporate the Extensions Manager, which simplified the process of enabling/disabling each extension individually. Extensions were often a source of instability and these changes made conflict resolution more friendly and assisted.
• Desktop accessory Control Panel becomes the folder Control Panels (Control Panels in the English version, located in the System Folder and accessible to the user via an alias of the Apple menu). The control panels themselves become separate files, stored within this directory.
• The Apple menu (previously showed only desktop accessories collected resources DRVR file/case System) now lists the contents of the directory Items Apple menu (Apple Menu Items) including alias. Desktop accessories, originally designed to provide a pseudo multitasking, are no longer necessary as true multitasking exists natively. Its technology is disapproved, and System 7 treats them the same as other applications. Desktop accessories now run in their own process instead of borrowing from the host application process.
• The Applications menu, a list of running applications, formerly located at the end of the Apple menu under MultiFinder, now has its own menu on the right. In addition, Hide/Show technology is introduced, allowing the user to hide applications from the view while still running.
• Help balloon, an accessory identification system similar to tooltips.
• AppleScript, a scripting language to automate tasks. While it is fairly complex for application programmers support it, it is very popular among users, and today there is an updated version as part of Mac OS X.
• AppleEvents - They support AppleScript with a new model of high-level events to be sent to applications, along with help to also work on the AppleTalk network.
• QuickDraw of 32 bits, called enduring images of true color ("true color"), is included as standard. It was previously available as an extension of the system. QuickDraw is used in Mac OS for quick on-screen drawing.
• Publish and Subscribe - This feature allows data published by one application to be imported (subscribed) by another and the data to be updated dynamically. Programmers complained that the API was unmanageable, and relatively few applications ended up supporting it.
• Virtual memory - This technology, already in use in other computers, allows to use part of the hard disk as if it were physical RAM, dumping the parts of memory not in use at that time and recovering them when necessary.
• TrueType vector fonts - Until then all the fonts of the Macintosh were Bitmap, or a set of bitmap screen fonts paired with PostScript vector fonts for the printer. TrueType offers for the first time a single font format that appeared the same on screen and on paper. This technology was recognized as important as launching a TrueType extension for System 6, it was also launched, together with an updated Font/DA Mover desktop accessory engine capable of installing the new font class in the System 6 System file.
• A new user interface full of color. Although this feature was made as an improvement of the visual interface, it was optional. On machines without the ability to display color, or in which the monochrome mode would have been set in the preferences, the interface returns to the black and white mode of previous versions. Only a few objects were colored: the scroll bars, for example, had a new look, but the buttons remained black and white.
• A new API, Sound Manager version 3.0, replaces the old ad hoc APIs. The new API offers a significantly improved hardware abstraction layer and higher playback quality. Although technically it is not a new feature of System 7 (these features were already available in System 6.0.7), Sound Manager 3.0 was the first implementation of this technology to extend it to most Mac users.
• System 7 paved the way for a 32-bit address space, replacing the previous 24-bit one. This process involved converting all routines of the operating system code to 32-bit pointers and the previous system addresses used the upper bits as flags (indicators). This change was called "32-bit clean". While System 7 itself was 32 bits, many existing machines and thousands of applications in use were not, so it took a while to complete the process. To facilitate the transition to the Memory control panel, it incorporated a switch to disable this feature, taking into account compatibility with old applications.

Software

System 7 was the first version of Mac OS that required a hard drive because of the large size of installed files that did not fit on a 1.44 MB floppy disk.

Later versions of System 7, specifically System 7.5 and 7.6, come with a directory of utilities that brought extras such as AppleScript, Disk Copy, QuickDraw GX Extras and QuickTime Movie Player, in addition to other applications that could be installed later, manually.

MS-DOS and Microsoft Windows compatibility

System 7.0 and 7.1 offered a utility called Apple File Exchange, which provided access to diskettes in MS-DOS and Apple II format. System 7 Pro, System 7.5 and later came with PC Exchange, previously a separate product, which allowed the system to mount floppy disks formatted in DOS and Windows on the desktop in the same way as Macintosh format disks.

System 7 can also read discs in HPFS format and allows users to access PC networks allowing communication.

Third-party software such as SoftPC allows compatibility with MS-DOS and Microsoft Windows programs, while others such as Connectix Virtual PC (today Microsoft Virtual PC) allow the Mac to run Windows and earlier versions of Mac OS through emulation. Others approach the issue via hardware using expansion cards with an Intel x86 processor and its own memory (the rest is mapped to Mac resources). Apple launches a series of devices with the last name DOS Compatible that bring one of these cards as standard (with an Intel 80486 or an Intel Pentium).

Release History

After System 7 was released, 7.0.1 was a minor re-release given in October 1991. A patch called "System 7 Tune-Up" followed the previous one, and minor updates followed throughout its life.

Although there were several updates that were added, due to the long period that System 7 had life. Most of the changes were improvements, to the existing software. At that time they did not focus much on security but on the stability of applications.