Hugh Pickens writes writes: "The Wall Street Journal reports that Hewlet Packard's HP-12C financial calculator has remained outwardly unchanged since its introduction in 1981. "Once you learned it on the 12C, there was no need to change," says David Carter, chief investment officer of New York wealth-management firm Lenox Advisors, who has owned his 12C for 22 years and still keeps it on his desk. "It's not like the math was changing." The 12C, which costs $70 on HP's website, is HP's best-selling calculator of all time, though the company won't reveal how many units it has sold over the years and the 12C still uses on an unconventional mathematical notation called "Reverse Polish Notation," which eschews parentheses and equal signs in an effort to run long calculations more efficiently which may be one reason users are reluctant to switch and tends to render the calculator mystifying to the novice user. New employees in financial services businesses quickly learn that ignorance of the 12C can flash more warning signs than a scuffed pair of shoes. "The guy with the totally beat-up HP-12C — you know he's actually done things in business," says James Granberry, a student at Vanderbilt University's Owen Graduate School of Management. "And then there's the young guy who looks like he may have put on his suit for the first time—with a graphing calculator." The HP-12C is one of only four calculators permissible in the Chartered Financial Analyst exams, the others being its sister, the HP-12C Platinum, and the Texas Instruments BA II Plus and BA II Plus Professional."