1967 · Microprogrammed Printing Calculator · Work 929 of 1,871
A university mathematics institute in Franconia on an autumn morning, on a laboratory table a boxy calculator fifty-five centimetres wide with a light grey-white case, on top a dark green hood with a white paper roll under a clear lid, at the front on a green field a block of cream keys and a block of black keys with one red key, every key plain, smooth and unmarked, a small red lamp glowing in a black strip above them, a hand in a tweed jacket sleeve feeding a thin shiny steel strip with rows of small round holes into a narrow slot at the side, morning mist in tall windows.
What it was used for
The Diehl Combitron was a programmable desk calculator; 2 of them were in use at the mathematics institute of the University of Erlangen-Nuremberg; the Erlangen computer science collection lists the machine under object number I1151 and both examples as working. The Deutsches Museum holds a programmable desk calculator "DIEHL combitron" of 1966, 26.5 kg, 250 by 550 by 430 mm. What the working environment looked like is shown by the Science Museum Group's holding of the successor model: a combitron S with a dilector paper tape reader, a tape punch, spare tape and printer paper. According to Frank Eggebrecht's account of Diehl's office machine production, the machine was shown at the Hanover fair in 1966, delivered from the summer of 1966 and built until 1968; internally it was model 301.
What was new
The Combitron did not carry its arithmetic rules hard-wired: at power-on the instruction level was read from a punched tape into the delay-line store - as microcode from a punched steel tape according to Rick Bensene, read by a photocell according to technikum29. Storage was a magnetostrictive delay line: 42 m of nickel wire according to Eggebrecht, in which the data circulate as sound pulses - switch off and they are gone. Program memory 66 steps, 16 digits, 20 keys, and according to Bensene only 142 transistors. The precedence holds only within national borders: on its English page technikum29 writes of the first operating programmable desk calculator built and sold in Germany; Olivetti's Programma 101 had already been presented in October 1965, with the same storage technique and 120 program steps.
What the sources leave open: The year in the work title is 1967, but the sources say 1966: Eggebrecht (delivery from summer 1966), Deutsches Museum, the Erlangen computer science collection, technikum29 and the Old Calculator Museum. 1967 is documented for the retrofitted paper tape interface. Price in DM and units built are not documented; Bensene calls it the first completely microcoded calculator only with reservation ("I believe").
Connections
Every connection names its kind. “Forerunner” on its own would be a claim.