Chapter 35 PILOT, the NBS multicomputer system 445

The system is designed to operate with a wide variety of input-output devices, both digital and analog.

Input readers and printers. Flexowriter units and paper-tape readers and punches will be available in the initial installation. Punched card input readers and high-speed printers, along with their auxiliary controls, may be attached to the format controller in the manner indicated in the preceding paragraph.

Display. Two types of displays are provided for: (1) pilot-light display of data and control information in the various registers and flip-flops throughout the system, in order to aid the rapid diagnosis of equipment malfunctions of programming faults, and (2) picture-tube display of real-time data stored in the internal memory of the system. This kinematic diagram type of display is very important when performing dynamic simulation operations which require visual presentation of the simulated data in real-time to the human operators.

Manual-monitor control. The term "manual-monitor" was coined at NBS several years ago to describe certain types of control operations that are initiated either manually by the machine operator or by the machine itself under conditions which are specified by means of external switch settings. The former is referred to as a manual operation and the latter is called a monitor operation because the machine must monitor its internal program to determine precisely when the operation should be performed. The type of operation to be performed as well as the conditions under which it is to be performed are specified by means of external switch settings.

This feature provides for convenient communication between the data-processor and the operator, and allows the operator to monitor the progress of the program automatically, to insert new data and instructions, and to withdraw intermediate results conveniently, without need for advance preparation of special programs. This is particularly useful in debugging programs and in checking equipment malfunctions.

Monitor operations are performed by the machine whenever the conditions specified by the external switch settings occur in the course of the program; e.g., every time the program refers to a new instruction, any time the program refers to an instruction to which a special monitor breakpoint symbol (e-digits) is attached, any time an arithmetic overflow occurs, etc. By pairing a particular type of manual-monitor operation with a selected set of conditions, a variety of special composite operations can be performed.

Remote controls. Manual-monitor operations can be specified and initiated by external devices as well as by human operators. Since all of the external switch settings control only d-c voltages, the external devices can even be remote from the machine itself, and from a distance, via ordinary electrical transmission lines, they can exercise supervisory control over the internal program of the machine. This makes it possible to harness together two or more remotely located data-processing machines, and have them work together co-operatively on a common task. Each member of such an interconnected network of separate data processors is free at any time to initiate and dispatch special control orders to any of its partners in the system. As a consequence, the supervisory control over the common task may be shared among the various members of the system, and may be passed back and forth from one machine to the other as the need arises.

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