is the product of a company named Soroban Engineering. It uses an IBM Model B Electric typewriter mechanism, modified by the addition of switches to detect keypresses, and solenoids to activate the typebars. It uses a traditional typebar mechanism, not the "golfball" IBM Selectric typewriter mechanism, which was not introduced until the next year. Lettercase is selected by raising and lowering the massive type basket. The Soroban is equipped with a two-color inked ribbon (red and black), and the interface allows color selection. Programs commonly use color-coding to distinguish user input from machine responses. The Soroban mechanism is unreliable and prone to jamming, particularly when shifting case or changing ribbon color. Offline devices are typically Friden Flexowriters that have been specially built to operate with the FIO-DEC character coding used by the PDP-1. Like the console typewriter, these are built around a typing mechanism that is mechanically the same as an IBM Electric typewriter. However, Flexowriters are highly reliable and were often used for long unattended printing sessions. Flexowriters have electromechanical paper tape punches and readers which operate synchronously with the typewriter mechanism. Typing rates are about ten characters per second. A typical PDP-1 operating procedure is to output text to punched paper tape using the PDP-1's "high speed" (60-character-per-second) Teletype model BRPE punch, then to hand carry the tape to a Flexowriter for offline printing. In later years, DECtape drives were added to some PDP-1 systems, as a more convenient method of backing up programs and data, and to enable early time-sharing. This latter application usually requires a secondary storage medium for swapping programs and data in and out of core memory, without requiring manual intervention. For this purpose, DECtapes are far superior to paper tapes, in terms of reliability, durability, and speed. Early hard disks were expensive and notoriously unreliable; if available and working, they are used primarily for speed of swapping, and not for permanent file storage. Graphics display The Type 30 Precision CRT display is a point plotting display device capable of addressing 1024 by 1024 addressable locations at a rate of 20,000 points per second. A special "Display One Point On CRT" instruction is used to build up images, which have to be refreshed many times per second. The CRT, which was originally developed for use in radar, is in diameter and uses a long-persistence P7 phosphor. A light pen can be used with the