Business Package II (Bus-Pak II) Reference Manual

This document serves as a comprehensive reference manual for Bus-Pak II, a computer system designed for data processing operations on either the PDP-4 or PDP-7 computing system. It aims to simplify business-oriented computer functions, making them accessible even to programmers with minimal experience.

Bus-Pak II operates on a character-by-character basis and features a powerful instruction set, including advanced editing capabilities, two modes of indexing (single and double), and extensive input/output control. The system requires 8K core storage, a paper tape reader-punch, and Teletype I/O, with optional support for card readers/punches, magnetic tape, DECtape (for Micro-Disk simulation), and high-speed printers.

The manual outlines two operational modes: "Run" for normal program execution and "Single Instruction" for debugging. It describes the system's memory organization, addressing schemes (including indirect addressing), and double precision arithmetic with 15 accumulators. It also covers the use of program counters, sense switches, and internal program switches for flow control.

A significant portion of the document is dedicated to detailing the Bus-Pak II instruction set, which is categorized into:

• Basic Control: For system initialization, program transfer, and basic operations.
• Data Manipulation: For clearing, moving, and expanding character data, as well as character zone manipulation.
• Logical Control: For testing characters, searching, and managing program and sense switches.
• Arithmetic: For operations on 15 double precision accumulators, including addition, subtraction, multiplication, and division.
• Accumulator Shift: For decimal point alignment in arithmetic operations.
• Editing Features: For automatic punctuation of numeric data in reports (e.g., dollar signs, commas, decimal points, asterisk protection).
• Comparison Instructions: For alphanumeric and numeric data comparisons.
• Indexing Control: For modifying addresses using index registers.
• Input/Output: Instructions for various peripherals like Teletype, punched cards, high-speed printers, magnetic tape, and Micro-Disk.
• Storage and Retrieval: For storing and retrieving subroutines and data on DECtape.
• Checkpoint and Restart: To allow job resumption after interruptions.
• Subroutine Control: For defining and transferring control to subroutines.

The manual also provides guidance on program preparation using a symbolic language, detailing assembler features, error messages, and procedures for loading the assembler and object programs. Appendices include a character code chart, instruction list, error messages, forbidden labels, and a coding sheet.