Samsung SGH-I530 Manual page 201

Using Calculator
202
Clears the last number you entered. If you
make a mistake while entering a number in
the middle of a calculation, you can use this
button to reenter the number without starting
the calculation over.
Places the current number into memory. Each
new number you enter with the M+ button is
added to the total already stored in memory.
The number you add can be either a
calculated value or any number you enter by
pressing the number buttons. Tapping this
button has no effect on the current calculation
(or series of calculations); it merely places the
value into memory until it is recalled.
Recalls the stored value from memory and
inserts it into the current calculation.
Clears any value that is stored in the
Calculator memory.
During a calculation, calculates a percentage
and allows you to use the resulting value in
the equation.
Calculates the square root of a number. Enter
the number, and then tap the square root
button.
Toggles the current number between a
negative and positive value. If you want to
enter a negative number, enter the number
first and then tap this button.