CalComp 565 drum plotter

The CalComp 565 is a drum plotter made by California Computer Products (CalComp) and sold from the early 1960s.¹ IBM sold the same machine as the IBM 1627 Model 1.² Artists in the United States and Sweden drew on it, or on its IBM version, in the 1960s and 1970s.^3, 4, 5

The company

Two engineers, Gene Seid and Robert Morton, built a prototype plotter in Los Angeles from 1953. With three others they incorporated California Computer Products in 1958 and set up in a garage in Downey, California. In the company's account it developed the world's first drum plotter in 1959. By 1961 the 565 was selling well enough for CalComp to go public.¹

How it draws

The paper is a roll with holes along its edges, fed over a drum with pins. When the drum turns, the paper moves up or down under the pen. The pen sits on a carriage that travels left and right across the paper. Every signal from the computer moves the carriage, the paper or both by one step of 1/100 inch (0.254 mm), or raises or lowers the pen. For the 1627 Model 1, IBM gives a drawing width of 11 inches on paper 120 feet long and up to 18,000 steps a minute.⁶

Since paper and pen can move together, there are eight possible moves: along the two axes and along the four diagonals.^2, 6 A line at any other angle has to be drawn as a staircase of these moves, and the computer must decide which move comes next, step by step. The University of Amsterdam's computer museum gives a different step, 0.1 mm at 250 steps a second, for its own 565.⁷

Bresenham's line

In 1962 Jack Bresenham at IBM wrote a program for an IBM 1401 that drove an IBM 1627, choosing the steps for a straight line without any multiplication or division.² He published the method in 1965 as "Algorithm for Computer Control of a Digital Plotter". It is now known as Bresenham's line algorithm and is used to draw lines with pixels.⁸

Artists on the 565

At Ohio State University, Charles Csuri drew Sine Curve Man Three (1967) on a CalComp 565, with an IBM 7094 computer and punched cards.³

The Swedish designer Astrid Sampe worked with the IBM programmer Sten Kallin. The Art Institute of Chicago credits her textile Computer Colonne (1975) to Sampe "with computer programmer Sten Kallin and IBM Plotter 1627".⁴ Kallin also worked with the artist Sture Johannesson from 1970 to 1975. Their works were computed on an IBM 1130 without a screen, fed with punched cards, and drawn on a CalComp drum plotter on a 30 cm paper roll.⁵ Both stories are told in Computer art in Sweden and in the notes on Astrid Sampe and the IBM 1130.

Where to see one

The University of Amsterdam's computer museum has two 565s. One was used at the university's Van der Waals physics laboratory; the museum restored its wiring and has drawn the Newell Teapot on it.⁷

A pen told where to go one move at a time is still how plotters work: see HP-GL and JAEV's text on plotter art. Olof Broström's Unverified Air at JAEV is stored as files for a pen plotter, one drawing a day.⁹