Addendum to "The Focus Number System"

In 1971 Kinsbury and Rayner, publishing under the title "Digital Filtering Using Logarithmic Arithmetic" [1] disclosed a sign-plus-logarithm number system, and a means of performing addition through single dimensional lookup using the formula c = b + F(a − b). The system was demonstrated on a computer. In 1975 Swartzlander and Alexopoulos disclosed Kinsbury\´s logarithmic arithmetic as "The Sign/Logarithm Number System" [2]. In 1977, without knowledge of prior art, we reinvented the wheel a third time, dubbing it "Focus," after the focus of resolution around the zero origin [3]. We wish now to acknowledge Kinsbury and Rayner as the pioneer authors, and also Swartzlander and Alexopoulos as prior to our publication.