February 6, 1940
Design begins of the Lake-Hamilton punch for preparing the sequence tape and the value tape for interpolation.
June-August 1940
Aiken works at Endicott with Lake and Hamilton in checking suggested changes to the machine's functional requirements. Aiken also instructs IBM mathematics classes during his stay.
October 1940
Aiken visits Endicott.
November 1940
Aiken visits Endicott.
November 15, 1940
Aiken advises Lake that he has shown Lake's relay to the Harvard faculty.
November 21, 1940
Aiken informs Lake that he has shown photographs of the panel and tape mechanism to the Harvard faculty.
March 6, 1941
Aiken sends Hamilton 36 logarithms and 21 sine values to be stored in the machine, and outlines the mathematical requirements for interpolation.
April 1941
Aiken assumes duties as a lieutenant commander in the U.S. Naval Reserve.
April 14, 1941
Hamilton tells Aiken that he and Durfee have conceived a counter on the functional panel for the purpose of adding or subtracting amounts in determining the final tape position. Hamilton asks Aiken's advice on the columnar capacity of this counter.
May 24, 1941
Aiken visits Endicott to discuss various phases of the project. He indicates that his new Navy duties will limit his involvement with the machine and suggests that R.V.D. Campbell of Harvard be assigned as his representative.
February 5, 1942
Hamilton and Campbell visit Aiken at Yorktown, Virginia, to discuss progress on the machine.
March 23, 1942
Campbell provides Hamilton with the values of the powers of 10 needed for computing anti-logorithms. The values are immediately wired into the machine.
April 11, 1942
Campbell recommends to Hamilton changes in the design affecting the calculation of exponential logarithms, sines and interpolation. The changes are adopted.
September 1942
Hamilton is assigned to war-related projects but continues to work on the machine in his "spare time."
January 1, 1943
The "Calculating Machine" successfully runs a test problem ("... in reference to a graph of the time required to build up the current in an inductive circuit based on an equation which required the machine to multiply, divide, add, subtract, compute logarithms and anti-logarithms."*)
1943
Lake and Durfee devote more of their efforts to testing the machine because of Hamilton's war-related work.
Late 1943
The machine is demonstrated to IBM customer administrative, customer engineering and systems service students.
December 8, 1943
The Calculator is demonstrated to Harvard faculty at Endicott.
* Extracts from an August 1944 internal IBM report.
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