Operator Precedence Rules:
A few operators have precedence over the others. For illustration, in the expression 4 + 5 * 3, the multiplication takes the precedence over addition, therefore at first 5 is multiplied by 3, then 4 is added to the result. Use of parentheses can change the precedence in an expression:
>> 4 + 5 * 3
>> (4 + 5) * 3
In a given precedence level, the expressions are computed from left to right (this is termed as the associativity).
Nested parentheses are the parentheses inside of others; the expression in the inner parentheses is computed first. For illustration, in the expression 5 - (6 *(4 + 2)), at first the addition is performed, then multiplication, and finally the subtraction to result in -31. Parentheses can also be simply used to make an expression clearer. For illustration, in the expression ((4 + (3 * 5))-1) the parentheses are not essential, but are used to present the order in which the expression will be computed.
For the operators which have been covered so far, the precedence is as shown below (from the maximum to the minimum):
*, /, \ all multiplication and division
+, - addition and subtraction