What are the major differences between versions of the Macintosh operating system?

In all cases, successive versions of Mac OS and Mac OS X have incorporated "under the hood" changes such as improved performance and stability, bug fixes, and in later releases, increased PowerPC nativity. In addition, the major releases included more obvious changes as described below:

Mac OS 7.0.x (several releases) (1991)

• 32-bit addressing for access to more than 8 megabytes of RAM
  
  
• Support for virtual memory on those computers that can use it
  
  
• Apple Events, a language used by applications to communicate with each other
  
  
• The MultiFinder, renamed the Finder, improved and simplified
  
  
• A Find utility incorporated into the Finder for locating files
  
  
• Ability to create aliases of items
  
  
• Ability to use File Sharing to share information between computers on a network
  
  
• Introduction of Balloon Help
  
  
• Introduction of Drag and Drop

Mac OS 7.1.x (several releases) (1992-1994)

• Introduction of WorldScript for improved multilingual support
  
  
• Fonts stored in their own Fonts folder rather than within the System Folder
  
  
• Introduction of Thread Manager for improved multitasking

Mac OS 7.5.x (several releases) (1994-1996)

• 32-bit addressing always turned on
  
  
• Some user interface improvements such as a menu bar clock, WindowShade, hierarchical Apple menus, and Finder windows that become accented when a file is dragged over them
  
  
• The AppleScript scripting language for automating tasks
  
  
• Improved Find File capability
  
  
• Apple Guide for improved help
  
  
• PC Exchange, which greatly simplifies working with DOS formatted disks
  
  
• Macintosh Easy Open to help open files for which the original application is not available
  
  
• Introduction of Open Transport (7.5.2)
  
  
• Comments in Info windows not removed when the desktop is rebuilt (7.5.3)

Mac OS 7.6.x (two releases) (Spring 1997)

• Requires a 32-bit clean 68030 processor or better
  
  
• Support for MacTCP removed
  
  
• Many references to "Macintosh" changed to "Mac OS" in response to the availability of Macintosh compatible clones

Mac OS 8.0 (Fall 1997)

• Requires a 68040 or PowerPC processor
  
  
• Numerous user interface improvements, including a revamped appearance, pop-up menus, custom folder views, desktop pictures, spring-loaded folders, contextual menus, sticky menus, and reorganized Finder menus; many of the control panels are reorganized, simplified, or incorporated into the Finder or System Folder
  
  
• Finder now multithreaded, allowing it to perform more than one task at once (e.g., emptying the trash while moving a file)
  
  
• Internet setup assistant for simplifying the task of setting up an Internet connection

Mac OS 8.1 (Spring 1998)

• Includes support for the Macintosh Extended File Format (HFS+), which increases the minimum and maximum file sizes
  
  
• Support for DVD-ROM drives
  
  
• Support for Windows 95 long filenames

Mac OS 8.5.x (two releases) (Fall 1998)

• Requires a PowerPC processor
  
  
• Introduces Sherlock, a powerful volume and Internet searching utility that replaces Find File
  
  
• AppleScript rewritten to be PowerPC native, greatly improving performance
  
  
• Ability to anti-alias all text on the screen
  
  
• Built-in application switcher and "tear off" Application menu
  
  
• HTML-based help system
  
  
• Interface enhancements such as smart scrolling, resizable Finder columns, 32-bit icons, icon tags, themes, and URL "aliases"

Mac OS 8.6 (Spring 1999)

• Built-in nanokernel that improves performance and reduces CPU power usage
  
  
• Newer computers (e.g., iMac, "blue and white" Power Macintosh G3/G4, "bronze" PowerBook G3, iBook) have the capability to boot off the network if an appropriate server is present.
  
  
• Game Sprockets included with the operating system (formerly a separate install)
  
  
• Improvements to Sherlock, LaserWriter 8, DVD-RAM, FireWire, Speech Recognition, and other components

Mac OS 9.0.x (two releases) (Fall 1999)

• Support for multiple users, storing individual preferences for each and with several levels of access
  
  
• Improved security with the Keychain (stores passwords), voiceprint authentication, and encrypted file transfers
  
  
• File sharing via TCP/IP with another Mac OS computer without the need for AppleShare IP
  
  
• Sherlock, dubbed Sherlock 2, updated for performance and capability
  
  
• Ability to automatically download software updates from the Internet and install them
  
  
• Support for Carbon and Carbonized applications

Mac OS 9.1 (Spring 2001)

• Several changes for improved compatibility with Mac OS X, including a slightly reorganized folder structure, OS X-aware Startup Disk control panel
  
  
• USB printer sharing over TCP/IP
  
  
• Apple File Security increased to 128-bit encryption
  
  
• Finder shortcuts to empty the trash, add to favorites, and show folder view options

Mac OS 9.2.x (three releases) (Fall 2001)

• Improved performance in the Classic environment of Mac OS X

Mac OS X 10.0.x "Cheetah" (four releases and numerous updates) (Spring 2001)

• Completely new operating system based on technologies acquired from NeXT, Inc.; features include protected memory, preemptive multitasking, multithreading, and symmetric multiprocessing
  
  
• Aqua, a new graphical user interface
  
  
• Darwin, the operating system's Unix foundation; built on the Mach microkernel
  
  
• Quartz, the PDF-based engine for rendering two-dimensional entities such as icons and windows
  
  
• Carbon, Cocoa, and Java, the three types of native graphical applications for Mac OS X

Mac OS X 10.1.x "Puma" (five releases and numerous updates) (Fall 2001)

• Improved performance, stability, and functionality
  
  
• Reintroduced missing OS 9 features: DVD playback, CD burning, AppleShare over AppleTalk, keyboard shortcuts for display brightness and sound volume
  
  
• The ability to connect to WebDAV and Windows file servers

Mac OS X 10.2.x "Jaguar" (eight releases and numerous updates) (Summer 2002)

• Improved performance, stability, and functionality
  
  
• Quartz Extreme, which uses your video card to improve performance of window moves, resizes, and the like; Quartz Extreme is not supported on older computers.
  
  
• Reintroduced missing OS 9 features: universal access, spring-loaded folders, USB printer sharing, AirPort and Airport Extreme software base station
  
  
• Built-in support for connecting to VPN servers via PPTP
  
  
• Rendezvous, for accessing resources via TCP/IP without configuration
  
  
• Inkwell, handwriting recognition using a graphics tablet
  
  
• Sherlock enhanced and refocused as an online tool
  
  
• Find utility integrated into the Finder

Mac OS X 10.3.x "Panther" (five releases and numerous updates) (Fall 2003)

• Improved performance, stability, and functionality
  
  
• Reintroduced missing OS 9 feature: labels
  
  
• Exposé, to easily navigate through a cluttered desktop by displaying open windows as selectable thumbnails
  
  
• Fast user switching, which allows for multiple accounts to be logged in at the same time
  
  
• FileVault, which encrypts the entire contents of home folders
  
  
• Built-in support for connecting to VPN servers via IPsec
  
  
• Font Book, for improved font management
  
  
• Improved support and integration for sending and receiving faxes

Mac OS X 10.4.x "Tiger" (Spring 2005)

• Unix-based architecture, for increased stability and security
  
  
• Spotlight, to instantly locate anything (e.g., images, email messages, applications) on your computer
  
  
• Dashboard, a readily accessible collection of mini-programs called "Widgets" that provide information about weather, stocks, and more
  
  
• Safari RSS, a new version of the popular web browser that includes a built-in RSS reader
  
  
• iChat AV, with the added ability to hold multi-party audio and video conferences
  
  
• Automator, to automate repetitive computing tasks without programming knowledge
  
  
• Mail, with integrated Spotlight searching and Smart Folders to help you manage your email

Also see:

• For Mac OS X, where can I obtain updates and new releases?
• What version of Mac OS X does my Mac computer support?
• For Mac OS and Mac OS X, what is Sherlock and how do I use it?
• In Mac OS and Mac OS X, how do I find out what version of the operating system I have?