Microtape

This document provides a comprehensive overview of the Microtape system, consisting of the Type 555 Dual Tape Transport and the Type 550 Tape Control unit. Designed as a cost-effective, reliable in-out and updating device, the system features fixed position addressing, bi-directional operation, and redundant phase recording for high reliability. The document details the hardware's technical specifications, explains the tape format—including timing, mark, and data tracks—and outlines the available programming subroutines for the PDP-1 and PDP-4 computers. Furthermore, it provides an instruction set, operational flag definitions, and guidance on error handling for developers using the system.