Assignment Operators

The assignment operator = assigns an lvalue (a variable) on the left with the result of the rvalue (a variable or expression) on the right:

    int x = 10; 
    x = x + 10;

The first line declares an integer and initializes it to 10. The second line alters the variable by adding another 10 to it, so now the variable x has a value of 20. This is the assignment. C++ allows you to change the value of a variable based on the variable's value using an abbreviated syntax. The previous lines can be written as follows:

    int x = 10; 
    x += 10;

An increment operator such as this (and the decrement operator) can be applied to integers and floating-point types. If the operator is applied to a pointer, then the operand indicates how many whole items addresses the pointer is changed by. For example, if an int is 4 bytes and you add 10 to an int pointer, the actual pointer value is incremented by 40 (10 times 4 bytes).

In addition to the increment (+=) and decrement (-=) assignments, you can have assignments for multiply (*=), divide (/=), and remainder (%=). All of these except for the last one (%=) can be used for both floating-point types and integers. The remainder assignment can only be used on integers.

You can also perform bitwise assignment operations on integers: left shift (<<=), right shift (>>=), bitwise AND (&=), bitwise OR (|=), and bitwise exclusive OR (^=). It usually only makes sense to apply these to unsigned integers. So, multiplying by eight can be carried out by both of these two lines:

    i *= 8; 
    i <<= 3;