Recorded Demonstration
Ames Laboratory,
Department of Energy,
ISU,
Ames, Iowa
 Completed ABC Replica
 Demonstration 
The picture at the left shows the digital storage oscilloscopes that
were connected to the first three coefficient memory brushes to
display the actual data in the machine during operation of the ABC.
The picture at the right shows the machine in roughly the same
orientation as the diagrams and
sketches of the Progress and
Diagrams page.
Operators Panel

Operator's Controls

The operator's panel for the ABC is shown above. On the top row,
looking left to right, are these buttons, switches, and indicators:
 Add/Sub Mode button
 Base 10 Card Read button
 Transfer CA (Memory Drum 1) to KA (Memory Drum 2) button
 Set of 6 Coefficient Select Switches (one switch for each
bank of five coefficients)
 Reading Base 10 Card Light
 Coefficient Elimination In Progress Light
 Base 10 Output In Progress Light
 Voltmeter
In the second row from the top:
 Base 2 Read In Progress Light
 Add/Sub Mode Selected Lights (Add Mode light is above Sub
Mode light)
 Select Card Reader Input Switch: Selects input from either
Base 2 or Base 10 readers
 Unused Switch
 IBM Card Read Switch: Selects circuits to handle negative
decimal number inputs from the Base 10 card reader
 Base 10 Output Switch: Selects circuits to handle Base 10
output on the odometer
 Positive Number Light: ON if the coefficient selected via
the top row of pegs is positive
 Negative Number Light: ON if the coefficient selected via
the top row of pegs is negative
 Power Supply Select Switch (for the voltmeter above)
And the third row from the top:
 Base 2 Output Button: Starts a write of the CA [Memory Drum
1] contents to paper on the Base 2 "punch"
 Base 2 Input Button: Starts a read of the Base 2 input into
CA [Memory Drum 1]
 Go (Coefficient Eliminate) Button: Begin computation and
compute until the coefficient, selected by the second row of pegs, is
zero
 Clear KA (Memory Drum 2) Switch: Set all bits to 0
 Clear CA (Memory Drum 1) Switch: Set all bits to 0
The bottom half of the operator's panel is dedicated to two sets
of thirty pegs. The top set of pegs selects the coefficient for which
Carry/Borrow Overflow is detected, and the bottom set of pegs
selects the coefficient for which Zero is detected. Two
special jumper wires, one for each of the rows of pegs, are inserted
to select the appropriate coefficient.
Demonstration

Dennis Sailsbury tapes while Charles Schorb executes a computation

The ABC had traveled to Washington, D.C. in October, 1997 for a
demonstration at the National Press Club. It then toured the state of
Iowa during the winter and spring seasons. Despite logging thousands
of miles since its demonstration in Washington, D.C., the computer was
in fine shape when it returned to its "home" at B40 Spedding Hall May
19, 1998.
The operation of the AtanasoffBerry Computer replica was demonstrated
and taped on video at the end of May, 1998 for production of an ABC
tutorial video. For the demonstration, the ABC computer successfully
solved the system of equations
x  3y = 11
2x + 4y = 8
giving the results x = 2
and y = 3
.


John Erickson looks over the base 10 conversion drum

Guy Helmer, Charles Shorb, and John Gustafson pose with the
ABC

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by ghelmer