<P> The 24 channels of the input tape were divided into three fields of eight channels . Each accumulator, each set of switches, and the registers associated with the input, output, and arithmetic units were assigned a unique identifying index number . These numbers were represented in binary on the control tape . The first field was the binary index of the result of the operation, the second was the source datum for the operation and the third field was a code for the operation to be performed . </P> <P> In 1928 L.J. Comrie was the first to turn IBM "punched - card equipment to scientific use: computation of astronomical tables by the method of finite differences, as envisioned by Babbage 100 years earlier for his Difference Engine". Very soon after, IBM started to modify its tabulators to facilitate this kind of computation . One of these tabulators, built in 1931, was The Columbia Difference Tabulator </P> <P> John von Neumann had a team at Los Alamos that used "modified IBM punched - card machines" to determine the effects of implosion . On 29 March 1944, he demanded to run certain problems regarding implosion on the Mark I. In early August 1944 he arrived with two mathematicians to write a simulation program to study the implosion of the first atomic bomb . </P> <P> The Los Alamos group completed its work in a much shorter time than the Cambridge group . However, the punched - card machine operation computed values to six decimal places, whereas the Mark I computed values to eighteen decimal places . Additionally, Mark I integrated the partial differential equation at a much smaller interval size (or smaller mesh) and so...achieved far greater precision . </P>

Who devised harvard mark 1 what was it used for