Microsoft Agent was a technology developed by Microsoft which employed animated characters, text-to-speech engines, and speech recognition software to enhance interaction with computer users. Thus it was an example of an embodied agent. It came preinstalled as part of Windows 98 through Windows Vista. It was not included with Windows 7 but can be downloaded from Microsoft. It was completely discontinued in Windows 8. Microsoft Agent functionality was exposed as an ActiveX control that can be used by web pages. The theory behind this software came from work on social interfaces by Clifford Nass and Byron Reeves at Stanford's Center for the Study of Language and Information. Version history Interactive character technology was first introduced in Microsoft Bob, which used an early version of Agent technology internally referred to as "Microsoft Actor." It was the code used in the initial version of the Office Assistant in Office 97. Microsoft Agent was subsequently created by Tandy Trower in an attempt to offer technology that was more flexible and available to third-party developers to include in their applications and web pages. The software release also included four interactive characters as well as a utility that enables developers to assemble their own characters and interactions. Microsoft Agent replaced the original Microsoft Actor code in Office 2000, although this use did not include Agent's much-touted speech synthesis or recognition capabilities or any of the four Microsoft Agent characters. Instead the Office team created their own characters including one dubbed "Clippit" or "Clippy". However, Bob Actors or Office 97 assistants are incompatible with Office 2000 and later versions, and vice versa. The current version of Microsoft Agent was quietly released on MSDN in 1997. Technology Microsoft Agent characters are stored in files of the .ACS extension, and can be stored in a number of compressed .ACF files for better World Wide Web distribution. Microsoft Office 97 and Microsoft Bob Actor characters are stored in files of the .ACT extension. Microsoft Agent character definition files are stored in files of the .ACD file extension, and are generated by the Microsoft Agent Character Editor. The speech engine itself is driven by the Microsoft Speech API (SAPI), version 4 and above. Microsoft SAPI provides a control panel for easily installing and switching between various available Text to Speech and Speech to Text engines, as well as voice training and scoring systems to improve the quality and accuracy of