A coordinate processor for a computer system having an absolute position pointing device (10) such as a touch sensitive display screen comprises stimulus detection means (200) for detecting a tactile stimulus of an absolute position pointing device (10) and directed to a point within a data display area (610) of a computer system. The processor further comprises coordinate locking means (210-320) for locking a current cursor position to the point within the display area corresponding to the tactile stimulus in response to said stimulus exceeding a predetermined threshold value. The processor permits the computer system to distinguish a stimulus of the pointing device (10) for repositioning the cursor within the data display area (610) from a stimulus of the pointing device (10) for issuing a button click command to the computer system. The processor may be embodied in an electronic logic circuit within a pointing device adapter portion of the computer system. Equally, the coordinate processor may be in the form of a central processing unit operating under the control of a computer program.

An additional status display of a touch panel on a CRT will maximize the operator's eye contact with the CRT while retaining the ability to select from the panel even though it is removed from the CRT and possibly located in another plane.

A "double-touch" input method is described that is particularly suitable for use as a substitute for a "double-click" input from a mouse or trackball, and that is particularly suitable for use with a touch panel. Briefly, the input method involves contacting a touch panel at a first location (for example, over an area where an icon is displayed) with a first finger. Before a predetermined period of time T.sub.wait elapses, a second finger "taps" the panel at a second location. The location tapped by the second finger is greater than a predetermined distance from the first location tapped by the first finger. In addition, the tap by the second finger is shorter than a second predetermined period of time T.sub.tap. After the tap by the second finger, the first finger is still in contact with the touch panel. The position of the first finger after the tap should be within a predetermined range of its position just prior to the tap. Apparatus in the form of a device driver is described for detecting a double touch input.

An advanced control room complex for a nuclear power plant, including a discrete indicator and alarm system (72) which is nuclear qualified for rapid response to changes in plant parameters and a component control system (64) which together provide a discrete monitoring and control capability at a panel (14-22, 26, 28) in the control room (10). A separate data processing system (70), which need not be nuclear qualified, provides integrated and overview information to the control room and to each panel, through CRTs (84) and a large, overhead integrated process status overview board (24). The discrete indicator and alarm system (72) and the data processing system (70) receive inputs from common plant sensors and validate the sensor outputs to arrive at a representative value of the parameter for use by the operator during both normal and accident conditions, thereby avoiding the need for him to assimilate data from each sensor individually. The integrated process status board (24) is at the apex of an information hierarchy that extends through four levels and provides access at each panel to the full display hierarchy. The control room panels are preferably of a modular construction, permitting the definition of inputs and outputs, the man machine interface, and the plant specific algorithms, to proceed in parallel with the fabrication of the panels, the installation of the equipment and the generic testing thereof.

The present invention provides virtual keyboard which can be used at the same number of operations as on a conventional keyboard and can allow a natural input operation at a minimized load. The virtual keyboard comprises a liquid crystal display for displaying thereon a keyboard having special keys and general keys, a transparent pressure-sensitive panel superimposed on the display and a computing portion that, when a special key and a general key on a pressure-sensitive panel are pushed at a time, detects the coordinate of a middle point between the two pushed positions from outputs of the pressure-sensitive panel, calculates a general key position from the special key point and the middle point and outputs a code corresponding to that position.