Description of using calculator

Summ using the following rule:"First multiplication and division (from left to right), then summation and subtraction(from left to right)."

Input:

1. Using interface.

2. Using digit keyboard (NEED TURN ON NUM LOCK). where operations: "delete -> AC" "ctrl -> +/-" "alt -> %" " , -> ." "Enter -> =" " * -> x", "/ -> /", " - -> -", " + -> +".