HP-55
Encyclopedia
The HP-55 was a programmable handheld calculator; a lower-cost alternative to the HP-65. Introduced by Hewlett-Packard
in 1975, it featured twenty storage registers and room for 49 keystroke instructions. Its outward appearance was identical to the HP-65, except that a few key functions were different and that it did not have a magnetic card reader/writer. Like all Hewlett-Packard calculators of the era and most since, the HP-55 used reverse Polish notation
(RPN) and a four-level automatic operand stack
.
Bill Hewlett's design requirement was that the calculator should fit in his shirt pocket. That is one reason for the tapered depth of the calculator. The documentation for the programs in the calculator is very complete, including algorithms for hundreds of applications, including the solutions of differential equations, stock price estimation, statistics, and so forth.
Hewlett-Packard
Hewlett-Packard Company or HP is an American multinational information technology corporation headquartered in Palo Alto, California, USA that provides products, technologies, softwares, solutions and services to consumers, small- and medium-sized businesses and large enterprises, including...
in 1975, it featured twenty storage registers and room for 49 keystroke instructions. Its outward appearance was identical to the HP-65, except that a few key functions were different and that it did not have a magnetic card reader/writer. Like all Hewlett-Packard calculators of the era and most since, the HP-55 used reverse Polish notation
Reverse Polish notation
Reverse Polish notation is a mathematical notation wherein every operator follows all of its operands, in contrast to Polish notation, which puts the operator in the prefix position. It is also known as Postfix notation and is parenthesis-free as long as operator arities are fixed...
(RPN) and a four-level automatic operand stack
Stack (data structure)
In computer science, a stack is a last in, first out abstract data type and linear data structure. A stack can have any abstract data type as an element, but is characterized by only three fundamental operations: push, pop and stack top. The push operation adds a new item to the top of the stack,...
.
Bill Hewlett's design requirement was that the calculator should fit in his shirt pocket. That is one reason for the tapered depth of the calculator. The documentation for the programs in the calculator is very complete, including algorithms for hundreds of applications, including the solutions of differential equations, stock price estimation, statistics, and so forth.
External links
- The HP-55 at an unofficial Hewlett-Packard museum (MyCalcDB).
- 1975 HP Calculator Christmas Guide
- HP-55 page at the unofficial Museum of HP Calculators