Gestalt was the name of a system call introduced into the Apple Macintosh operating system System Software 6.0.4 in 1989 to allow applications to dynamically query what capabilities were present in the running system configuration. By this time, the pace of Mac development had produced such a proliferation of hardware configurations and hardware and software add-ons from Apple and third parties that a simple version check was no longer enough to determine the features of the system. Instead, Gestalt maintains a dynamically-extensible table of OSType selector codes.