User:RTC/scratch

One of the inspirations for ENIAC was the mechanical analog Bush Differential Analyzer. It influenced both the architecture and programming method chosen. However, although ENIAC could have been programmed as a DDA, there is no evidence that it ever actually was. The theory of DDAs was not developed until 1949, one year after ENIAC had been reconfigured as a stored program computer.

The first DDA built was the Magnetic Drum Digital Differential Analyzer of 1950.

Block diagram of a basic DDA Integrator. Δx causes y to be added to or subtracted from S, Δy causes y to be incremented or decremented, and ΔS is caused by an overflow or underflow of the S acumulator.

$y^{*}=y\pm \sum \Delta y$

$S^{*}=S\pm y^{*}$