The iPhone calculator is a simple calculator with minimal functions.
To do a simple calculation, enter in a number, then an operation, then another number, and then the = button. For instance, to add 13+86 you would enter 1 then 3, then +, then 8 and 6, then =.
To calculate a restaurant tip, you would enter the total bill, then X for multiplication, then . and 2 to find 20% of the bill. Then press = to get the result.
There is also a memory function. Press m+ to store the current number in memory. Once it is there, you can use m+ to add to that number. Use m- to subtract from memory. When you want to get the result that is in memory, use mr/mc. Press it again to clear memory. When a number is stored in memory, the mr/mc button is outlined.
The c button will clear the current operation.
The calculator will perform operations in standard mathematical order. So 3+4×2 will return 11. This is because multiplication and division are performed before addition and subtraction. To do the equivalent of 3+4 multiplied by 2, you would type 3+4=x2=.
Note that dividing by 0 does not return an error in the iPhone calculator. It returns 0.
Pressing the = button will repeat the last operation. So 3+4×2 will return 11. Press = again and you get 22, then 44, then 88, and so on.