Schematic diagram in hard copy relating to the computer CSIRAC.

C.I.S. is the abbreviation for Completed Iinstruction Store. This stored the 16 instructions that have just been executed. It is a diagnostic tool for seeking the cause of an error. It allows the operator to review the last sixteen instructions leading to the error.

A single delay line was dedicated to this purpose. The sixteen instructions were shown on the cathode ray screens on the console.

The emulator developed by John Spencer includes the C.I.S.

A schematic diagram shows the detailed connections between all the components in a circuit. Such diagrams were used to build circuits and later for testing. For CSIRAC, the most common components were vacuum tubes (valves), capacitors and resistors. Schematic diagrams are also known as circuit diagrams.

Technical details:
Schematic Diagram. Subsystem: Control
Pencil, Drawing Size B

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