There are various ways in which calculators interpret keystrokes. These can be categorized into two main types:On a single-step or immediate-execution calculator, the user presses a key for each operation, calculating all the intermediate results, before the final value is shown.
On an expression or formula calculator, one types in an expression and then presses a key, such as "=" or "Enter", to evaluate the expression. There are various systems for typing in an expression, as described below.
A Sharp scientific calculator using infix notation. Note the formula on the dot-matrix line above and the answer on the seven-segment line below, as well as the arrow keys allowing the entry to be reviewed and edited.
The Hewlett-Packard Voyager series of calculators all use RPN input. The "Enter" key is used here to push the value on the display onto the stack.
This printing calculator made by Sharp uses ten-key notation. Notice the size and placement of the keys, including the extra-large "+/=" and the red "-/=" keys.
A Casio Natural Display scientific calculator displaying mixed fractions and their decimal equivalents in pretty-printing.
A scientific calculator is an electronic calculator, either desktop or handheld, designed to perform calculations using basic and complex mathematical operations and functions. They have completely replaced slide rules as well as books of mathematical tables and are used in both educational and professional settings.
Casio fx-991DE X - A modern Digital calculator from Casio with a dot matrix "Natural Textbook" LCD
Casio fx-77, a solar-powered digital calculator from the 1980s using a single-line LCD
HP-35, the world's first scientific pocket calculator, was introduced in 1972 by Hewlett-Packard. It used reverse Polish notation and an LED display.
TI SR-50