DIAL-MS BUILD Program Description

This document describes the BUILD routine, a core component of the LAP6-DIAL operating system for the PDP-12 computer. The primary function of BUILD is to customize the DIAL-MS system for a specific hardware configuration by identifying available I/O devices and generating the necessary device-specific I/O routines.

The BUILD process is composed of three logical parts:

1. Device Detection: Code responsible for identifying which I/O devices are present and constructing tables for the I/O controller.
2. I/O Controller: A field-independent dispatcher that directs read and write calls to the appropriate device handlers. It maintains an internal table (MTABLE) that maps logical unit numbers (including system-specific units like 100 for the DIAL-MS system itself, 110 for source, and 111 for binary) to physical device handlers and applies any required block number adjustments.
3. Individual I/O Handlers: Low-level, page-independent routines, each designed to control a specific physical device (e.g., LINCtape, RF08, DF32, and RK08 disks). These handlers operate without needing external routines or constants.

The INITIALIZATION phase, beginning at block 310 of the DIAL-MS Editor, loads a prototype I/O controller and default LINCtape handler. It then dynamically checks for other devices, updates the device table accordingly, and relocates new device handlers in memory if additional devices are detected. This configured I/O system is then saved, and the DIAL-MS Editor is bootstrapped. The document includes detailed flow diagrams and program listings illustrating these processes.