Object Pascal is an extension to the Pascal programming language that provides object-oriented features such as classes and methods.
The language was originally developed by Apple Computer as Clascal for the Lisa Workshop development system. As Lisa gave way to Macintosh, Apple collaborated with Niklaus Wirth, the author of Pascal, to develop an officially standardized version of Clascal. This was renamed Object Pascal. Through the mid-1980s, Object Pascal was the primary programming language for early versions of the MacApp application framework. The language lost its place as the primary development language on the Mac in 1991 with the release of the C++-based MacApp 3.0. Official support ended in 1996.
Symantec also developed a compiler for Object Pascal for their THINK Pascal product, which could compile programs much faster than Apple's own Macintosh Programmer's Workshop (MPW). Symantec then developed the THINK Class Library (TCL), based on MacApp concepts, which could be called from both Object Pascal as well as THINK C. The THINK suite largely displaced MPW as the primary development platform on the Mac in the late 1980s.
Symantec ported Object Pascal to the PC, and developed a similar object framework on that platform. In contrast to TCL, which eventually migrated to C++, the PC libraries remained primarily based on Pascal.