The Diablo 630 is a discontinued daisy wheel style computer printer sold by the Diablo Data Systems division of the Xerox Corporation beginning in 1980. The printer is capable of letter-quality printing; that is, its print quality is equivalent to the quality of an IBM Selectric typewriter or printer, the de facto quality standard of the time. Overview The printer is capable of this quality at a nominal speed of 30 characters per second (roughly twice the speed of the Selectric). Several technologies were introduced to enable this quality and speed: The lightweight daisy wheel is rotated by a closed-loop servo and can be positioned rapidly and accurately. Because the wheel can turn in either direction, the next character is never more than 180° away from the previous character (and related characters are grouped together so the average "seek" is much less than 180°). Like the "typeball" element on a Selectric, the daisy wheel can be easily changed, allowing for a wide variety of fonts and character pitches. Some models can use wheels with two rows of characters, allowing for the machine to print in two different languages or with a large set of special symbols. The printer uses cartridge-loaded ribbons; both an economical endless cloth ribbon and a high-quality single-use film ribbon were available, with colored ribbons provided by third parties. By contrast, Selectric-based printers can use only one type of ribbon—cloth or single-use carbon film—and were almost always equipped for the former for economic reasons. The carriage is also servo-controlled and the printer can print with the carriage moving either forward or backward, saving most of the time that would otherwise be spent executing carriage returns. The servo control of the carriage permitted the use of proportionally-spaced fonts, wherein each character does not have to occupy the same amount of horizontal space. Unlike Selectric-based printers, daisy wheel printers support the entire ASCII printing character set. Bidirectional paper motion is similarly servo-controlled, allowing quick printing of subscripts and superscripts as well as fast slewing past white space. Servo control of both paper and carriage permitted the unit to be used for plotting, with resolution of 120×48 steps per inch. This was popular enough that special daisy wheels were made with a reinforced period (.), the character most often used for plotting. The logic permits simultaneous motion of the wheel, the carriage, and the paper. The hammer automatically strikes only