To add some specificity to gamegoblin's reference, I quote from page 28 of the IBM 1401 Data Processing System: Reference Manual[1]: The two factors to be comb

To add some specificity to gamegoblin's reference, I quote from page 28 of the IBM 1401 Data Processing System: Reference Manual[1]: The two factors to be combined are added within core storage without the use of special accumulators or counters. Because any storage area can be used as an accumulator field, the capacity for performing arithmetic functions is not limited by standard-size accumulators or by a predetermined number of accumulators within the system. [1] http://bitsavers.informatik.uni-stuttgart.de/pdf/ibm/140x/A24-1403-5_1401_Reference_Apr62.pdf http://bitsavers.informatik.uni-stuttgart.de/pdf/ibm/140x/A2...