Classic Environment
Classic OS applications running alongside native OS X applications.
Maintainer:	Apple Computer
Latest release:	1.9 / March 21, 2005
OS:	Mac OS X
Use:	Software layer
License:	Proprietary
Website:	Apple.com

Classic, or Classic Environment, is a hardware and software abstraction layer in Mac OS X that allows applications compatible with Mac OS 9 to run on the OS X operating system. It utilizes a Mac OS 9 System Folder, and a New World ROM file to bridge the differences between the older PowerPC Macintosh platforms and the XNU kernel environment. Classic has been a key element of Apple's strategy to replace the "classic" Mac OS (versions 9 and below) with Mac OS X as the standard operating system used by Macintosh computers, by eliminating the need to use the older OS directly. It is the only way to run "classic" applications on an Apple G5 system, which cannot boot Mac OS 9 or earlier. Classic is not supported on versions of Mac OS X that run on Apple systems incorporating Intel microprocessors, which will include all new Apple systems by the end of 2006.^[1] Image File history File links Classic_Logo. ... Image File history File links Download high resolution version (1024x768, 452 KB) Summary Screenshot demonstrating how Classic allows native and Classic applications to run side-by-side. ... This article or section does not cite its references or sources. ... Software maintenance is one of the activities in software engineering, and is the process of enhancing and optimizing deployed software (software release), as well as remedying defects. ... Apple Computer, Inc. ... A software release is to create a new version of the system or program and release it to the user community. ... March 21, 2005 Icelands parliament, Alþingi, votes to grant fugitive U.S. chess champion Bobby Fischer Icelandic citizenship. ... An operating system (OS) is an essential software program that manages the hardware and software resources of a computer. ... This article or section does not cite its references or sources. ... A software license is a type of proprietary or gratuitous license as well as a memorandum of contract between a producer and a user of computer software — sometimes called an End User License Agreement (EULA) — that specifies the perimeters of the permission granted by the owner to the user. ... Proprietary software is software that has restrictions on using and copying it, usually enforced by a proprietor. ... This page as shown in the aol 9. ... Computer hardware is the physical part of a computer, including the digital circuitry, as distinguished from the computer software that executes within the hardware. ... Computer software (or simply software) refers to one or more computer programs and data held in the storage of a computer for some purpose. ... An abstraction layer is a way of hiding the implementation details of a particular set of functionality. ... This article or section does not cite its references or sources. ... Application software is a loosely defined subclass of computer software that employs the capabilities of a computer directly to a task that the user wishes to perform. ... Sherlock 2 for Mac OS 9 with the new metallic appearance Mac OS 9 was the last version of what has since become known as the classic Macintosh Operating System (Mac OS), introduced by Apple Computer on October 23, 1999. ... The System Folders icon The System Folder is the directory in classic versions of Mac OS (those prior to OS X) that holds various files required for the system to operate, such as fonts, system extensions, control panels, and preferences. ... This article needs to be cleaned up to conform to a higher standard of quality. ... PowerPC is a RISC microprocessor architecture created by the 1991 Apple-IBM-Motorola alliance, known as AIM. Originally intended for personal computers, PowerPC CPUs have since become popular embedded and high-performance processors as well. ... In computing, a platform describes some sort of framework, either in hardware or software, which allows software to run. ... XNU is the name of the kernel that Apple acquired and developed for use in the Mac OS X operating system and released as open source as part of the Darwin operating system. ... In computer science, the kernel is the core piece of most operating systems. ... The first Macintosh computer, introduced in 1984, upgraded to a 512K Fat Mac. The Macintosh, or Mac, is a line of personal computers designed, developed, manufactured, and marketed by Apple Computer. ... In computing, the PowerPC 970 and the PowerPC 970FX, also known as PowerPC G5, are 64-bit processors in the PowerPC family from IBM, which was introduced in 2002. ... Sherlock 2 for Mac OS 9 with the new metallic appearance Mac OS 9 was the last version of what has since become known as the classic Macintosh Operating System (Mac OS), introduced by Apple Computer on October 23, 1999. ... The Apple Intel transition is an announced change in the architecture of the Macintosh platform. ...

Classic is a descendant of Rhapsody's "Blue Box" emulation layer, which served as a proof of concept. It can be loaded at login (for faster activation when needed later), on command, or whenever a Mac OS application that requires it is launched (to reduce the use of system resources when not needed). It requires a full version of Mac OS 9 to be installed on the system, and loads an instance of that OS in a sandbox environment, replacing some low-level system calls with equivalent calls to Mac OS X via updated system files and the Classic Support system enabler. This sandbox is used to launch all "classic" Mac OS applications—there is only one instance of the Classic process running for a given user, and only one user per machine may be running Classic at a time. a desktop showing a QuickTime movie and a drawing application Rhapsody was the code name given to Apple Computers next-generation operating system during the period of its development between Apples purchase of NeXT in late 1996 and the announcement of Mac OS X in 1998. ... A proof of concept is a short and/or incomplete realization of a certain method or idea(s) to demonstrate its feasibility. ... A login (also log in, log on, signon, sign on) is the process of accessing a computer system by identification of the user in order to obtain credentials to permit access. ... Sherlock 2 for Mac OS 9 with the new metallic appearance Mac OS 9 was the last version of what has since become known as the classic Macintosh Operating System (Mac OS), introduced by Apple Computer on October 23, 1999. ... For the Wikipedia sandbox for editing experiments see Wikipedia:Sandbox This article is about the computer security model. ... In computing, a system call is the mechanism used by an application program to request service from the operating system, or more specifically, the operating system kernel. ... In computing, a process is a running instance of a program, including all variables and other state. ...

If the "load-when-needed" option is selected, double clicking a "classic" application first launches Classic, which can be configured to appear in a window resembling the display of a computer booting into Mac OS 9. When Classic is finished loading, the application launches. When a "classic" application is in the foreground, the menu at the top of the screen changes to look like the older Mac OS system menu. Dialog boxes and other user-interface elements retain their traditional appearance. Mouse properties in GNOME, with a setting for double-click speed A double-click is the act of pressing a computer mouse button twice quickly without moving the mouse. ... An example of a graphical user interface in Windows XP, with the My Music window displayed A window is a visual area, usually rectangular in shape, containing some kind of user interface, displaying the output of and allowing input for one of a number of simultaneously running computer processes. ... In computing and telecommunications, a menu is a list of commands presented to an operator by a computer or communications system. ... Dialog boxes are special windows which are used by computer programs or by the operating system to display information to the user, or to get a response if needed. ...

Classic's compatibility is very good, provided the application using it does not require direct access to hardware or engage in full-screen drawing. However, it is not a perfect clone of Mac OS 9. The Finder included with Mac OS X v10.2 and later does not support the "Reveal Object" Apple event used by Mac OS 9 applications, causing the "Reveal In Finder" functionality for those applications to be lost. Early releases of Mac OS X 10.2 would often fail to draw window frames of Classic applications correctly. Additionally (somewhat to the surprise of end-users) Classic resurrected some older applications that had previously been unusable on the Macintosh Quadra and Power Macintosh series; this is because Mac OS X replaced Mac OS 9's virtual memory system with a more standard and less fragile implementation, and eliminated the Motorola 68040's split cache system. Mac OS X version 10. ... Apple Events are the canonical high-level interprocess communication mechanism in Mac OS, first appearing in System 7 and supported by every version since then, including Mac OS X. The starting point is a dynamically-typed, extensible descriptor format called an AEDesc, which is just an OSType code specifying the... Quadra 800 Quadra was the name used by Apple Computer for most of its Macintosh computers built around the Motorola 68040 CPU. The product manager for the Quadra family was Frank Casanova who was also the Product Manager for the Macintosh IIfx. ... Power Macintosh, or Power Mac, is the name of a line of Apple Macintosh personal computers based on various models of PowerPC microprocessors. ... The memory pages of the virtual address space seen by the process, may reside non-contiguously in primary, or even secondary storage. ... The Motorola 68040 is a microprocessor from Motorola. ...

Classic's performance is also generally acceptable, with a few exceptions. Most of an application is run directly as PowerPC code. (This is likely a major reason why Classic is not supported on Intel-based Macs.) Motorola 68k code is handled by the same Motorola 68LC040 emulator that Mac OS 9 uses. Some application functions are actually faster in Classic than under Mac OS 9 on equivalent hardware, due to performance improvements in the newer operating system's device drivers. These applications are largely those that use heavy disk processing, and as of 2005 most have been ported to Mac OS X. On the other hand, applications that rely on heavy processing and which did not share resources under Mac OS 9's co-operative multitasking model will be interrupted by other (non-Classic) processes under Mac OS X's preemptive multitasking. The greater processing power of most systems that run OS X (compared to systems intended to run Mac OS 8 or 9) helps to mitigate the performance degradation of Classic's emulation. In computing, a benchmark is the result of running a computer program, or a set of programs, in order to assess the relative performance of an object, by running a number of standard tests and trials against it. ... PowerPC is a RISC microprocessor architecture created by the 1991 Apple-IBM-Motorola alliance, known as AIM. Originally intended for personal computers, PowerPC CPUs have since become popular embedded and high-performance processors as well. ... A system of codes directly understandable by a computers CPU is termed this CPUs native or machine language. ... Motorola (NYSE: MOT) is an international communications company based in Schaumburg, Illinois, a Chicago suburb. ... The Motorola 680x0/0x0/m68k/68k/68K family of CISC microprocessor CPU chips were 32-bit from the start, and were the primary competition for the Intel x86 family of chips. ... The 68LC040 is a low cost version of the Motorola 68040 microprocessor with no FPU. This makes it less expensive and draw less power. ... An emulator reproducing a console games playable atmosphere on a Windows computer. ... A device driver, often called a driver for short, is a computer program that enables another program, typically an operating system (OS), to interact with a hardware device. ... 2005 is a common year starting on Saturday of the Gregorian calendar. ... In computer science, porting is the adaptation of a piece of software so that it will function in a different computing environment to that for which it was originally written. ... It has been suggested that this article or section be merged into Computer_multitasking#Cooperative_multitasking. ... Pre-emptive multitasking is a form of multitasking in which processes are not allowed to take an indefinitely long time to complete execution in the CPU. Each process, in turn, is granted a portion of CPU time (usually called a time slice, on the order of milliseconds). ... Mac OS 8 is a series of versions of the Mac OS that, although they introduced few remarkable new user features, supported a transition through major changes in the Apple Macintosh hardware platform. ...

The name "Classic" is sometimes used to refer to the application programming environment available to "classic" applications, to differentiate between programming for Mac OS X and the previous version of the Mac OS. For instance, software vendors that support Mac OS 9 and earlier via native applications (rather than Carbon applications) often refer to the pre-Mac OS X version as the "Classic" version, as "Mac OS" is increasingly assumed to mean "Mac OS X". Carbon is the codename of Apple Computers API for the Macintosh operating system, which permits a good degree of forward and backward compatibility between source code written to run on the classic Mac OS, and the newer Mac OS X. The APIs are published and accessed in the form...

See also

• Basilisk II
• SheepShaver
• Rosetta

History Basilisk II is an open source software emulator which emulates the 680x0-based Apple Macintosh computer on a variety of operating systems, including BeOS, Linux, Windows NT and Mac OS X. The last version of Mac OS that can be run within Basilisk II is Mac OS 8. ... SheepShaver is an open source PowerPC Apple Macintosh emulator originally designed for BeOS and Linux. ... Rosetta is a lightweight dynamic translation emulator for Mac OS X distributed by Apple. ...

References

1. ^ News.com, January 10 2006: Jobs: New Intel Macs are "screamers"