Abstract: In a dumb terminal to which an auxiliary device may be attached, improvements in display definitions. In the transfer of data between a host computer and the terminal or an auxiliary device, and in character generation memory. In the area of display definition, pages may be mapped onto the terminal's display memory and viewports may be mapped onto pages. Page and viewport definition are independent of each other and settable modes permit a viewport to follow the active position. In the area of transfer of data, the source of data for the host computer and the destination of data from the host computer may be specified independently. Improvements in flow control ensure that the host computer can always change the destination of data and gain control of the terminal. Improvements in access control ensure that neither the terminal nor the auxiliary device can monopolize transfer between it and the host.

Abstract: Protocols for communicating between a digital data processing system and a terminal. The terminal permits specification of attributes for characters, of fill characters and their attributes, of key board bit maps, and of different modes of specifying a group of shifted characters. The protocols include a protocol which takes another as an operand and specifies how the second protocol is to be executed, protocols which control the use of fill characters, a protocol which resets the attributes of a string of characters, protocols for shifting fields to the left and right and scrolling regions up and down, protocols which save and restore the current cursor state, protocols for loading bit maps and checking their correctness, a protocol for setting the current mode of specifying shifted characters, a protocol for setting the high bit of a following code, and a protocol for obtaining the attribute of the character at the current cursor position.