Commercial Instructions

This document provides a technical specification for the Commercial Instruction Set (CIS) for the DECsystem-10/20, originally approved by the Architecture Committee on March 22, 1979. The instruction set is designed to optimize COBOL performance by offering character string manipulation instructions and decimal arithmetic instructions. The document details the instruction formats, addressing modes (direct, deferred, direct subscripted, deferred subscripted, and immediate), opcode assignments, and general architectural conventions, including interrupt handling, arithmetic faults, and the use of the EXTEND instruction for execution. Appendices provide information on performance, extensions to the BIS instruction set, assembler notation guidelines, and a revision history.