1. In an information processing system including keyboard means for entering document data and document manipulation commands, processor means for operating upon said documents and means for displaying said documents, means for controlling operations of said system, comprising: document memory means for storing segments of a document being operated upon, document control means, including buffer means for transferring said document data between said document memory means and said keyboard and display means, document access means for storing and providing information identifying and locations in said document memory means of segments of a said document currently being operated upon, and information identifying the locations in said buffer means of said document data to be transferred between said document memory means and said keyboard and display means, document manipulation means, including memory means for storing and providing document operation routines for controlling document operations to be performed upon said document segments and said document data, supervisory control means, including system supervisory operation memory means for storing and providing supervisory operation routines for controlling supervisory operations of said system, and means responsive to operation of said keyboard means for providing operation vectors identifying document operations to be performed upon said document data and said document segments and supervisory operations to be performed by said system, said processor means being responsive to said operation vectors for reading and performing corresponding said document operation and supervisory operation routines, and responsive to said document operation routines for reading said location information from said document access means for locating said document segments and data to be operated upon in said document memory means and said buffer means, wherein, the only routines which perform operations upon said document segments residing in said document memory means are said document operation routines, said document operation routines access said document segments and data residing in said document memory means and said buffer means only through said location information residing in said document access means, and said document segments and data transferred between said document memory means and said keyboard and display means only through said buffer means.