Chapter 35 PILOT, the NBS multicomputer system 441
of the figure, (2) the primary storage, upper center; (3) the secondary computer and the secondary storage, right; (4) the input-output control, upper left; (5) the external storage units, upper far left; (6) the external input-output units such as readers, printers, and displays, lower far left; and (7) lower left, the external control containing the special features that facilitate communication with people and devices in the world outside the system which is remotely located if necessary. Interchanges of information between the system and the outside world can take place at any time, on a completely impromptu basis, at the instigation of either the system or the external world, or both acting jointly.
The primary computer, a high-speed general-purpose computer, contains both an arithmetic unit and a program control unit of considerable versatility. This computer can carry out a variety of high precision arithmetic and logical processing operations, in either binary or decimal code and in a wide variety of word lengths and formats. Its partner computer, the secondary computer, specializes in short-word operations, usually manipulations on address numbers or other "red-tape" information, which it supplies automatically as needed to the primary program. The third computer of the system, called the format controller (see input-output control in Fig. 1), is specially designed for carrying out editing, inspecting, and format-modifying operations on data that are flowing in or out of the internal memory via the peripheral external units of the system. All three computers, and all the external units of the system, share access privileges to the common high-speed internal memory, which is linked to the input-output and external storage units via independent trunks for effecting data-transfers. Transfers of data can take place between the external units, the memory units, and the computers concurrently without interrupting the progress of the computational program. Because of the flexibility of the format controller, incoming data can be accepted
Fig. 1. Over-all block diagram for PILOT.