Basic functions

Enter a number by typing digits; use the "." key to insert a decimal point.

To perform an operation, press the operation key, enter another number, then press "=". The pending operation is shown on the bottom line. Because the "7-segment"-style font does not have a "/" or "÷" character, "d" is shown to indicate a division operation.

To perform a percentage operation, press the operation key, enter another number, then press "%".

• The operation × number % multiplies by a percentage, 20 * 25% is 4.
• The operation + number % adds a percentage, 20 + 25% is 24.
• The operation - number % subtracts a percentage, 20 - 25% is 16.
• The operation ÷ number % divides by a percentage, 20 / 25% is 80.

Square Root

Press the √ key to compute the square root of the last number entered or calculated. For example, to calculate the "golden ratio" you can type: 1 + 5 √ / 2 which is equivalent to (1+√5)/2.

Clear and Backspace

The button marked C is a combination backspace/clear button. If a number has been entered, press backspace to erase it one digit at a time. If no number is entered (or the number has been erased) press it to clear the pending operation. If no number or operation is entered, press it to set the last number calculated to 0.0.

Pasting to a Host Computer

Hold fn and press = to paste the last number calculated to an attached computer.

Make it your own

The author had so many ideas and not enough time to implement them.

• The fn key exists to access just one special feature. There should be more! Do you want to add parentheses? Trig functions? Exponents? Go wild!
• Investigate 2/3/4 line layouts & experiment with different fonts
• Add a mode where it operates as a pure numeric keypad or macro pad
• Install a battery under the PCB so you can go mobile
• Use the udecimal library to upgrade to arbitrary-precision numbers