HP-41CX alphanumeric handheld computer

By the time the HP-41CX was introduced, it was called a computer rather than a calculator. It had more than twice as many built-in functions and three times as much memory capacity as the HP-41C.  When the HP-41C handheld calculator was introduced in 1979, it was the first calculator that could display alphabetic characters as well as numbers. But more importantly, it was fully programmable and expandable. For many people, the HP-41C was their introduction to computer programming.  It was less expensive than a personal computer, and—through the HP Interface Loop (HP-IL0)—it could be hooked up to a printer, plotter and mass-storage device. 

How to Change Commas to Decimal Point on HP 41c - FAQ