Browse Prior Art Database

Floating-Point Conversions Without Table Lookups

IP.com Disclosure Number: IPCOM000038320D
Original Publication Date: 1987-Jan-01
Included in the Prior Art Database: 2005-Jan-31

Publishing Venue

IBM

Related People

Authors:
Breed, LM Karp, AH [+details]

Abstract

This invention relates to a method for floating-point (FP) radix conversion in a nondecimal FP arithmetic processor. The method steps include (a) being responsive to a decimal-coded numeric signal value x and an integer p, multiplying p x log1610 = t; (b) partitioning t into an integer (r) and fractional (w) part; (c) converting value x to floating point form; (d) computing 2(4w); and (e) forming the product x2(4w) and adjusting the hexadecimal exponent by r. Decimal to Hexadecimal Conversion Given a decimal number of the form X x 10p, find a floating point number Z in the normal System/360 range such that Z x 16r = X x 10p, where p and r are integers. Let 10p = 16t so that t = plog1610. Define r = int(t) as the integer part of t, and w = t-r. Now .CE Z = X x 10p16-r = X x 16w = X x 24w .