The Hewlett-Packard Voyager series of calculators were introduced by Hewlett-Packard in 1981. All members of this series are programmable, use Reverse Polish Notation, and feature continuous memory. Nearly identical in appearance, each model provided different capabilities and was aimed at different user markets. Models The HP calculators Voyager series consisted of five models, some of which were manufactured in several variants (with years of production): HP-10C – basic scientific calculator (1982–1984). HP-11C – mid-range scientific calculator (1981–1989). HP-12C – business/financial calculator (1981–present). HP-15C – advanced scientific calculator (1982–1989, 2011). HP-16C – computer programmer's calculator (1982–1989). HP-10C The HP-10C is the last and lowest-featured calculator in this line, even though its number would suggest an earlier origin. The 10C was a basic scientific programmable calculator. While a useful general purpose RPN calculator, the HP-11C offered twice as much for only a slight increase in price. Designed to be an introductory calculator, it was still costly compared to the competition, and many looking at an HP would just step up to the better HP-11C. Poor sales led to a very short market life, making it one of the most difficult of the series to find today. HP-11C The HP-11C is a mid-range scientific programmable calculator. HP-12C The HP-12C is a popular financial calculator. It was such a successful model that Hewlett-Packard redesigned it from scratch, added several new functions, and introduced it as the HP 12c Platinum in 2003 as well as the HP 12c Prestige. Over the course of years, several anniversary editions of the calculator were produced as well. The HP-12C is HP's longest and best-selling product, in continual production since its introduction in 1981. HP-15C The HP-15C is a high-end scientific programmable with a root-solver and numerical integration, produced between 1982 and 1989. It is also able to handle complex numbers and matrix operations. Although long being discontinued its continued popularity among users triggered Hewlett-Packard to offer a HP 15c Limited Edition remake of the calculator in 2011. HP-16C The HP-16C is a computer programmer's calculator, designed to assist in debugging. It can display numbers in hexadecimal, decimal, octal and binary, and convert numbers from one base to another. A number of specialized functions are provided to assist the programmer, including left- and right-shifting, masking, and bitwise logical operations. HP has (as of 2015) never made another programmer's calculator, but has incorporated the 16C's functions in later calculator models.