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The Atanasoff - Berry - Computer
at the Computer History Museum

as of March 19, 2011

The reconstructed Atanasoff - Berry - Computer is on loan to the Computer History Museum, Mountain View, California.
It is displayed in the new (2011) formally presented (world class) display of artifacts called R|EVOLUTION.

The ABC is the first known device to use vacuum tubes for digital arithmetic work. Here is a display to the left of the ABC of a standardized arithmetic chassis using 7 vacuum tubes. To ease quick replacement in case of suspected trouble, the plug at the bottom contained all of the logical and power connections to the unit.

First a little orientation -


courtesy Alice R. Burks.
This is an annotated drawing from Burks & Burks.
Another view of the machine (in Iowa) is here

Views of the left, front, right. The rear is mostly obscured by a wall of the display area.

Views of the left
Left side
The two big drums, Keyboard & Counter, store 1500 bits each. Each drum stores 30 binary numbers of 50 bits each.
Conversion Drum. These brushes, electrically contacting the metal Conversion Drum, assist in converting the holes in the IBM card reader into binary for computation in the ABC.
More arithmetic chassis center, right is high voltage electronics to blast holes in the paper for intermediate result output.
Views of the front
The intermediate result "punch" and reader. The coin is a quarter for size reference.
This unit reads IBM cards, 5 numeric fields/card, into the ABC via the Decode drum. The yellow arrow points to the ABC output device, a ratcheting counter for the operator to read.
The operator reads this "odometer" to obtain the decimal value of the variable just computed. Note the ratcheting operated from the solenoid, and that the numbers go in different directions.
Views of the right
This synchronous motor drives all the mechanical systems in the ABC. It is synchronous so that the Positive cycle of the wall power sine wave is at the correct mechanical point for hole blasting for intermediate output.
Motor tag - 1/4 horsepower, 1800 RPM - exactly one revolution each two cycles of AC power.
Right side view
  • Motor left middle
  • Shaft hidden in middle horizontal L-bracket
  • Visible gear goes 1 revolution per second, provides timing for whole machine

If you have comments or suggestions, Send e-mail to Ed Thelen

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