The Console of PDP-3 has controls and indicators for the use of the operator. Fig. 4 is a close-up of the control panel of PDP-1, the 18 bit version of PDP-3. All computer flip-flops have indicator lights on the Console. These indicators are primarily for use when the machine has stopped or when the machine is being operated one step at a time. While the machine is running, the brightness of an indicator bears some relationship to the relative duty factor of that particular flip-flop.
Three registers of toggle switches are available on the Console. These are the Test Address (15 bits), the Test Word (36 bits), and the Sense Switches (6 bits). The first two are used in conjunction with the operating push buttons. The Sense Switches are present for manual intervention. The use of these switches is determined by the program (see [System Block Diagram] and [Skip Group Instructions]).
Operating Push Buttons
Start — When this switch is operated, the computer will start. The first instruction comes from the memory location indicated in the Test Address Switches.
Stop — The computer will come to a halt at the completion of the current memory cycle.
Continue — The computer will resume operation starting at the state indicated by the lights.
Examine — The contents of the memory register indicated in the Test Address will be displayed in the Accumulator and the Memory Buffer lights.
Deposit — The word selected by the Test Word Switches will be put in the memory location indicated by the Test Address Switches.
Read-In — When this switch is operated, the photoelectric paper tape reader will start operating in the Read-In mode. (see [Input-Output]).
In addition to the operating push buttons, there are several separate toggle switches.