PDP-15 SGEN-DOS Utility Program

This document describes the DOS-15 System Generator Utility Program, known as DOSGEN. It is an interactive tool designed for system managers to modify and maintain an existing DOS-15 system to suit specific installation requirements, rather than creating a new system from scratch.

DOSGEN guides the user through eight sequential sets of questions (identified A through H) to modify three fundamental areas of the system:

1. System Parameters (Section A): Allows configuration of settings such as API availability, teleprinter type, Master Identification Code (MIC), default buffer numbers and words per buffer, allocation of extra 4K memory pages, default file protection code, resident patch area size, page mode system setting, and line frequency (60/50 CPS).
2. I/O Devices and Handlers (Sections B, C, E): Enables users to delete, retain, or add I/O devices and their associated handlers and "skips" (interrupt service routines). It covers various device types like Card Readers, Paper Tape, DECtape, Disk Control, Line Printers, MAGtape, and Displays, and allows adjustment of specific device parameters.
3. System Programs (Sections D, F, G, H): Provides functionality to change the order of the system's interrupt skip chain (Section D), alter the number and assignments of .DAT slots (Section F), manage core-image system programs (like DOS15, PIP, MACRO, PATCH, UPDATE) including their overlays and buffer allocations (Section G), and add new core-image system programs and their overlays (Section H).

The manual outlines the process for building DOS-15 for the first time, starting with restoring the basic system using the DOSSAV program. This is followed by a preliminary DOSGEN run to delete unneeded components and set initial parameters. Subsequent steps detail how to customize the system for FORTRAN and Graphics, add source files, and perform a second DOSGEN run for further integration of system programs and devices using tools like PATCH and PIP.

DOSGEN operates by building new images of key system information blocks: SGNBLK, SYSBLK, COMBLK, and the Storage Allocation Table (SAT). It supports both interactive teleprinter command mode and batching command mode, includes checks for input validity, and provides restart points for question sets. Appendices offer detailed information on DOSSAV operations, directory listings (BNK, PAG, PER UFDs), handler source assembly parameters, and the internal structure of SYSBLK, COMBLK, and SGNBLK.