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 data type, together with a block of type-dependent data. For instance, the OSType code 'inte' indicated that the data was a four-byte signed integer in big-endian format. Apple Events are the foundation of the AppleEvent Object Model, which in turn is the foundation of AppleScript.