Hex Adder

This black and silver-colored aluminum adder has an aluminum stylus. The instrument fits in a black plastic sleeve with three identical paper charts. The adder has six columns and shows six-digit totals. The top part of the column is used for adding numbers, with 0 to 9 to A to F in each column. The letters represent 10 to 15 in a hexadecimal (base 16) number system. The lower part of the band is similarly divided and used for subtraction. The columns are notched at both top and bottom to allow for carrying and borrowing. Moving up a metal piece below the columns with the stylus clears the instrument.

The three sheets of paper are divided to inches along both edges. On the right edge, each inch is divided to 15 parts, and the divisions are numbered up to 159 (every third division actually has a number next to it). On the left edge, each inch is divided into 12 parts, and the parts are numbered up to 126. On the right-hand scale of each sheet, the space from 18 to 33 is marked, as is the space from 126 to 142. There also are single marks at 41 and 118. These sheets were used to measure either lines per inch or characters per inch in planning printouts.

According to the website of Hexco, Inc., the firm was started in 1967 by Tom and Linda Tarrant, both of whom had been system engineers with IBM. The HEX adder was the firm's first product. According to records of the U.S. Patent and Trademark Office, the term Hex Adder was first used in commerce in March 19, 1968 and trademarked February 4, 1969. As the mark on the instrument indicates that the name was trademarked, it seems likely that the instrument dates from about 1970. It was given to the Smithsonian by COBOL programmer Joan P. Nichols.

References: Website of Hexco, Inc., accessed March 2, 2010. Records of the U.S. Patent and Trademark Office.

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