Think C (stylized as THINK C; formerly Lightspeed C) is an extension of the C programming language for the classic Mac OS developed by Think Technologies, released first in mid-1986. THINK was founded by Andrew Singer, Frank Sinton & Mel Conway. The firm was later acquired by Symantec Corporation and the product continued to be developed by the original author, Michael Kahl. Versions 3 and later were essentially a subset of C++ and supported basic object-oriented programming (OOP) concepts such as single inheritance, and extensions to the C standard that conformed more closely to the needs of Mac OS programming. After version 6, the OOP facilities were expanded to a full C++ implementation, and the product was rebranded Symantec C++ starting version 7, then under development by different