PDP-11 Instruction Set

This document is a 1969 confidential preliminary specification for the PDP-11, a 16-bit small computer. It provides detailed technical information on the processor hardware architecture, including:

• Processor Registers: Description of the eight 16-bit hardware registers (Program Counter, Status Register, Accumulator, X-Register, Y-Register, and 'mini' registers).
• Memory Addressing: Details on various addressing modes, including relative, Page 0, full, immediate, 'mini', external, X-indexed, and Y-indexed addressing.
• Instruction Groups: Comprehensive breakdowns of machine instructions categorized into groups: Memory Reference (e.g., load, store, add, compare, and, jump), Operate, Conditional Jump, Add to Register, and External (input/output/control).