Tenkey Notation (adding Machine)
This input method first became popular with accountants paper tape adding machines. It generally makes the assumption that entered numbers are being summed, although other operations are supported. Each number entered is followed by its sign (+/-), and a running total is kept. An assumption is made that the last operand can be implicitly used next, so by just entering another + (for example), one will reuse the most recent operand. TenKey input mode is available in printing calculators from companies such as Sharp, and in software calculators like Judy's TenKey used by accounting firms. Online tenkey training and certification tools are available as well, and some businesses use tenkey typing speed as an employment criterion.
| Formula | Key strokes | Key stroke count |
|---|---|---|
| 1 + 2 × 3 = + T | 8 | |
| 3 0 SIN × 3 0 COS = | 8 | |
| 5 + 3 - T | 5 | |
| 1 5 + 1 0 + + + T | 9 |
Read more about this topic: Calculator Input Methods