Fred (File Replacement, Entry, and Deletion)

Summary

This document is a technical manual for FRED, a set of subroutines designed for the PDP-12 computer to manipulate indices for the LAP6-DIAL operating system. The software package facilitates file management tasks, specifically file replacement, entry, and deletion on LINCtape.

Key components of the document include:

• Overview and Environment: Describes the memory usage and operational requirements for FRED, which occupies two tape blocks and utilizes four LINC memory blocks.
• Usage Instructions: Outlines how to load and interface with FRED, detailing entry points for major routines (LOOKUP, ENTER, REPLACE, DELETE, READ, and WRITE). It provides code examples for calling these routines.
• Routine Descriptions: Provides in-depth technical explanations of how each routine functions, including parameter handling, index interaction, and space management algorithms.
• Flowcharts: Includes visual logic representations for the various operations to assist in understanding the program flow.
• Technical Appendices: Contains the full source code and a symbol table for the FRED subroutines, providing documentation on memory addresses, register definitions, and implementation details.