The Maniac III arithmetic system

Unlike most computers, for which there is a formal distinction between "fixed-point" and "floating-point" numbers, the University of Chicago Maniac III computer handles all numbers in a single format (exponent and coefficient, with the coefficient in general not normalized). This permits several types of arithmetic to be defined, which differ in that results are adjusted (coefficient scaled) according to different rules. These rules are classified in terms of "significant-digit," "normalized," "specified point" or "basic" characteristics. Since the operand format in all cases is the same, numbers can be processed by the various arithmetics without intermediate conversion, thus adding a dimension of flexibility to the computing process. This paper discusses the Maniac III arithmetic rules in some detail, showing how they embody the cited characteristics, and how consistent conventions for rounding, adjustment of zero and formation of low order parts are established. The trapping system used for the detection of anomalous results is also described.