Operators

You can perform calculations on values read by a C/C++ program. In addition to ordinary arithmetic, libraries provide functions such as sin, cos, and tan. Let's first look at the operators used most often in basic code.

Assignment and arithmetic

In mathematics, a = b + c expresses equality. In C/C++, it means calculate b + c and assign the result to a. For example, a = 1 + 2 stores 3 in a.

If a contains 3, printf("%d", a); replaces the %d placeholder with that value and prints 3. To compare whether a and b are equal, use a == b instead of assignment.

+  Addition        a = b + c   Assign the sum to a
-  Subtraction     a = b - c   Assign the difference to a
*  Multiplication  a = b * c   Assign the product to a
/  Division        a = b / c   Assign the quotient to a
%  Remainder       a = b % c   Assign the remainder to a

Integer division discards the fractional part. The % operator works with integer operands; it does not calculate a floating-point remainder. Also remember that % has a different role inside a formatted input/output string.

Compound assignment

a += b   Assign a + b to a
a -= b   Assign a - b to a
a *= b   Assign a * b to a
a /= b   Assign a / b to a
a %= b   Assign a % b to a

Comparisons

a == b   a is equal to b
a = b    Assign b to a (assignment, not comparison)
a != b   a is not equal to b
a <= b   a is less than or equal to b
a >= b   a is greater than or equal to b
a < b    a is less than b
a > b    a is greater than b

Prefix and postfix operators

a++   Use the previous value, then increment a by 1
++a   Increment a by 1, then use the new value
a--   Use the previous value, then decrement a by 1
--a   Decrement a by 1, then use the new value

Logical operators

a && b   Both a and b must be true (AND)
a || b   At least one of a or b must be true (OR)
!a       a is not true (NOT)
!b       b is not true (NOT)

An expression such as !a reverses its truth value: true becomes false, and false becomes true. These operators will appear more and more often as the lessons progress, so make sure you are comfortable with them.

Translation note: the operator reference blocks have been translated into English. The original compound-assignment table repeated += beside multiplication and division; those labels are corrected here.