Carbon (API)

Carbon was a primary application programming interface, or API, developed by Apple for Mac OS X. An API is a set of tools that allows software to communicate with an operating system. Carbon served a vital role in Apple's transition from the classic Mac OS to the modern Mac OS X platform. It provided a bridge for developers to move their existing software to a new environment. This process of moving older software to the new system was called "carbonizing" applications.

To understand how Carbon worked, we must look at the architecture of the system. Carbon was not an emulator, which is a program that pretends to be another system. Instead, it was a native API that ran directly on top of a Unix-like operating system. Carbon consisted of many libraries and functions organized into groups called Managers. Each Manager was responsible for a specific system service. For example, the File Manager handled opening and reading files on the disk. The Window Manager controlled the creation and positioning of windows on the screen. The Font Manager handled different text styles, while the Resource Manager managed icons and sounds.

Apple's path to creating Carbon involved a major change in strategy. In late 1996, Apple purchased the company NeXT. This led to a new operating system strategy based on the OPENSTEP platform. Initially, Apple planned to use an emulator called the "Blue Box" to run old software. Many developers were upset by this plan. They feared their code would be stuck in a "penalty box" that would never be updated. In 1998, Steve Jobs announced a new direction to provide a modern Mac OS. This resulted in the release of Carbon in 2000 to provide a real upgrade path.

Carbon and a newer system called Cocoa were designed to work as peers. To make this work, Apple created a shared foundation called Core Foundation, or CF. While Cocoa used the Objective-C language, Core Foundation was written in pure C. This allowed both systems to use the same underlying code. Apple even used a technique called "toll-free bridging" to help them work together without slowing down performance. Additionally, Apple developed a new graphics engine called Quartz. Quartz provided C API calls that both Carbon and Cocoa could use to draw images on the screen.

The transition from Carbon to Cocoa was a long process for many companies. Some developers found it difficult to rewrite their large amounts of legacy code. For instance, Adobe Photoshop was a famous Carbon application for many years. It was not finally updated to the Cocoa system until April 2010. Even Apple used Carbon for its own flagship software for a long time. The Finder application remained a Carbon app until 2009. Other major programs like iTunes and Final Cut Pro also relied on Carbon for many years before eventually moving to Cocoa.

Significant changes began to appear in 2007. When Apple released Mac OS X v10.5, they began the transition to 64-bit computing. However, Apple did not create a 64-bit version of Carbon during this time. This was a major turning point because it meant Carbon was limited in the new 64-bit environment. In 2012, with the release of OS X 10.8 Mountain Lion, Apple officially deprecated Carbon. This meant that while the API still worked, Apple would no longer add any new features or updates to it.

The end of Carbon came through a series of updates to the macOS system. On June 28, 2017, Apple announced that 32-bit software would no longer be supported on newer versions of the operating system. Because Carbon applications were 32-bit, they were at risk of becoming obsolete. Finally, with the release of macOS 10.15 Catalina, Apple officially removed support for 32-bit applications. This included all Carbon applications. Today, Cocoa remains the sole primary API for developing modern applications for the Mac platform.