MAC OS 7
Basic Overview:-System 7 (codenamed "Big Bang" and sometimes retroactively called Mac OS 7) is a single-user graphical user interface-based operating system for Macintosh computers. It was introduced on May 13, 1991 by Apple Computer. It succeeded System 6, and was the main Macintosh operating system until it was succeeded by Mac OS 8 in 1997. Features added with the System 7 release included virtual memory, personal file sharing, QuickTime, QuickDraw 3D, and an improved user interface.
"System 7" is often used generically to refer to all 7.x versions. With the release of version 7.6 in 1997, Apple officially renamed the operating system "Mac OS", a name which had first appeared on System 7.5.1's boot screen. System 7 was developed for Macs that used the Motorola 680x0 line of processors, but was ported to the PowerPC after Apple adopted the new processor.
Deep Introduction:-The development of the Macintosh "Systems" up to System 6 followed a fairly smooth progression with the addition of new features and relatively small changes and upgrades over time. Major additions were fairly limited, notably adding Color QuickDraw and MultiFinder in System 6. Some perspective on the scope of the changes can be seen by examining the official system documentation, Inside Macintosh. This initially shipped in three volumes, adding another to describe the changes introduced with the Mac Plus, and another for the Mac II and Mac SE.
These limited changes meant that the original Mac system remained largely as it was when initially introduced. That is, the machine was geared towards a single user and task running on a floppy disk based machine of extremely limited RAM. However, many of the assumptions of this model were no longer appropriate. Most notable among these was the single-tasking model, the replacement of which had first been examined in 1986's "Switcher" and then replaced outright with MultiFinder in System 5. Running MultiFinder normally required larger amount of RAM and a hard drive, but these were becoming common by the late 1980s.
While additions had been relatively limited, so had fixes to some of the underlying oddities of the system architecture. For instance, to support a limited form of multitasking, the original Mac OS supported small co-resident programs known as desk accessories which had to be installed into the Apple menu using special tools. If the system were able to support multiple tasks, this one-off solution would no longer be needed - desk accessories could simply be small programs, placed anywhere. Yet, as MultiFinder was still optional, such a step had not been taken. Numerous examples of this sort of problem could be found throughout the system.
Finally, the widespread adoption of hard drives and local area networks led to any number of new features being requested from users and developers. By the late 1980s, the list of new upgrades and suggested changes to the existing model was considerable.