C Arithmetic Operators
Arithmetic Operators
Arithmetic operators are used to perform common mathematical operations.
| Operator | Name | Description | Example | Try it |
|---|---|---|---|---|
| + | Addition | Adds together two values | x + y | Try it » |
| - | Subtraction | Subtracts one value from another | x - y | Try it » |
| * | Multiplication | Multiplies two values | x * y | Try it » |
| / | Division | Divides one value by another | x / y | Try it » |
| % | Modulus | Returns the division remainder | x % y | Try it » |
| ++ | Increment | Increases the value of a variable by 1 | ++x | Try it » |
| -- | Decrement | Decreases the value of a variable by 1 | --x | Try it » |
Here is an example using different arithmetic operators in one example:
Example
int x = 10;
int y = 3;
printf("%d\n", x + y); // 13
printf("%d\n", x - y); // 7
printf("%d\n", x * y); // 30
printf("%d\n", x / y); // 3
printf("%d\n", x % y); // 1
int z = 5;
++z;
printf("%d\n", z); // 6
--z;
printf("%d\n", z); // 5
Note: When dividing two integers in C, the result will also be an integer.
For example, 10 / 3 gives 3.
If you want a decimal result, use float or double values, like 10.0 / 3.
Example
int a = 10;
int b = 3;
printf("%d\n", a / b); // Integer division, result is 3
double c = 10.0;
double d = 3.0;
printf("%f\n", c / d); // Decimal division, result is 3.333...
Incrementing and Decrementing
Incrementing and decrementing are very common in programming, especially when working with counters, loops, and arrays (which you will learn more about in later chapters).
The ++ operator increases a value by 1, while the -- operator decreases a value by 1:
Sometimes, you might both increment and decrement the same variable. Remember that if you increase a value and later decrease it, it will go up by one and then back down by one - ending up where it started:
Example
int x = 5;
++x; // Increment x by 1 (x becomes 6)
--x; // Decrement x by 1 (x becomes 5 again)
printf("%d\n", x); // 5
Real Life Example: Counting People
Imagine you are building a program to count how many people enter and leave a room.
You can use ++ to increase the counter when someone enters,
and -- to decrease it when someone leaves:
Example
int peopleInRoom = 0;
// 3 people enter
peopleInRoom++;
peopleInRoom++;
peopleInRoom++;
printf("%d\n", peopleInRoom); // 3
// 1 person leaves
peopleInRoom--;
printf("%d\n", peopleInRoom); // 2
Prefix and Postfix
The ++ and -- operators can be written before the variable (prefix, like ++x) or after it (postfix, like x++).
On their own, both add 1 to x. The difference shows when you use the value in the same statement:
++xincreasesxfirst, and then uses the new valuex++uses the current value first, and then increasesx
Example
int x = 5;
int y = ++x; // x is increased first, then y gets 6
printf("x = %d, y = %d\n", x, y); // x = 6, y = 6
int a = 5;
int b = a++; // b gets 5 first, then a is increased
printf("a = %d, b = %d\n", a, b); // a = 6, b = 5
Visualize Prefix and Postfix
Choose an operator below to see in which order things happen:
Code
What happens
Output
Explanation
