HP-18C

The HP-18C was a business calculator with a new folding design and a dedicated alphabetic keyboard. It was HP's first algebraic pocket calculator. (HP previously used algebraic logic on desktop calculators, portable and desktop computers, and the HP-01 calculator watch.) Besides the basic business features of time value of money, cash flows etc., it had a clock with appointments, and a very powerful equation solver. It had 4 numbered registers, plus named lists.