C# Operators

Operators do work on values: they calculate, compare and combine them.

Arithmetic Operators

Operator	Meaning	Example	Result
`+`	Add	`12 + 5`	`17`
`-`	Subtract	`12 - 5`	`7`
`*`	Multiply	`12 * 5`	`60`
`/`	Divide	`12 / 5`	`2`
`%`	Remainder	`12 % 5`	`2`
`++`	Add 1	`x++`
`--`	Subtract 1	`x--`

Example

csharp

int totalDays = 45;
int weeks = totalDays / 7;
int days = totalDays % 7;
Console.WriteLine($"{weeks} weeks and {days} days");
Console.WriteLine(45 / 7.0);

Output

6 weeks and 3 days
6.428571428571429

Dividing two int values gives an int and drops the decimal part. Use at least one double (like 7.0) to get the decimal answer.

Assignment Operators

Operator	Same as
`x += 5`	`x = x + 5`
`x -= 5`	`x = x - 5`
`x *= 5`	`x = x * 5`
`x /= 5`	`x = x / 5`
`x %= 5`	`x = x % 5`

Example

csharp

int points = 100;
points += 50;   // bonus
points -= 30;   // penalty
points *= 2;    // double weekend
Console.WriteLine(points);

Output

Comparison Operators

These give a bool: True or False.

Operator	Meaning
`==`	Equal to
`!=`	Not equal to
`>` / `<`	Greater / less than
`>=` / `<=`	Greater or equal / less or equal

Logical Operators

&& and: both sides must be true
|| or: at least one side must be true
! not: reverses the value

Example

csharp

int age = 17;
bool withParent = true;

Console.WriteLine(age >= 18);
Console.WriteLine(age >= 18 || withParent);
Console.WriteLine(!withParent);

Output

False
True
False

The Math Class

C# has a built-in Math class for common calculations:

Method	Example	Result
`Math.Max(a, b)`	`Math.Max(4, 9)`	`9`
`Math.Min(a, b)`	`Math.Min(4, 9)`	`4`
`Math.Sqrt(x)`	`Math.Sqrt(64)`	`8`
`Math.Pow(x, y)`	`Math.Pow(2, 5)`	`32`
`Math.Round(x)`	`Math.Round(4.6)`	`5`
`Math.Abs(x)`	`Math.Abs(-7)`	`7`

Example

csharp

double bill = 2347.567;
Console.WriteLine(Math.Round(bill, 2));
Console.WriteLine(Math.Sqrt(144));

Output

2347.57
12

Order of Operations

*, / and % happen before + and -. Use brackets to be clear:

Example

csharp

int a = 6 + 4 * 2;     // 14
int b = (6 + 4) * 2;   // 20

Exercise

What does Console.WriteLine(20 % 6); print?

323.336