There are five mathematical operators:
addition (+),
subtraction (-),
multiplication ( *),
division (/), and
modulus (%).
Integer division differs from ordinary division.
Integer division produces only integers, so the remainder is dropped.
The value returned by 21 / 4 is 5.
The modulus operator % returns the remainder value of integer division, so 21 % 4 equals 1.
Floating-point division is ordinary division. The expression 21 / 4.0 equals 5.25.
C++ decides which division to perform based on the type of the operands.
If at least one operand is a floating-point variable or literal, the division is floating point. Otherwise, it is integer division.
The following expression adds 10 to the value of a variable named score:
score = score + 10;
This can be written more simply using the += self-assigned addition operator:
score += 10;
The self-assigned addition operator += adds the r-value to the l-value, and then assigns the result to the l-value.
There are self-assigned subtraction (-=), division (/=), multiplication ( *=), and modulus (%=) operators, as well.