C Operators

Operators perform actions on values, like adding, comparing or combining them.

Arithmetic Operators

Operator	Meaning	Example	Result
`+`	Add	`10 + 4`	`14`
`-`	Subtract	`10 - 4`	`6`
`*`	Multiply	`10 * 4`	`40`
`/`	Divide	`10 / 4`	`2`
`%`	Remainder	`10 % 4`	`2`
`++`	Add 1	`x++`
`--`	Subtract 1	`x--`

Example

#include <stdio.h>

int main(void) {
  int minutes = 135;
  int hours = minutes / 60;
  int left = minutes % 60;
  printf("%d hours and %d minutes\n", hours, left);
  return 0;
}

Output

2 hours and 15 minutes

% only works with whole numbers. A common use is checking if a number is even: n % 2 == 0.

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

#include <stdio.h>

int main(void) {
  int stock = 50;
  stock -= 12;   // sold 12
  stock += 30;   // new delivery
  stock++;       // one returned
  printf("Stock: %d\n", stock);
  return 0;
}

Output

Stock: 69

Comparison Operators

In C, a comparison gives 1 for true and 0 for false.

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

Example

#include <stdio.h>

int main(void) {
  int a = 8, b = 3;
  printf("%d\n", a > b);
  printf("%d\n", a == b);
  return 0;
}

Output

1
0

Logical Operators

&& (and): true when both conditions are true
|| (or): true when at least one is true
! (not): reverses the result

Example

int age = 22;
int hasTicket = 1;
printf("%d\n", age >= 18 && hasTicket);   // prints 1
printf("%d\n", !hasTicket);               // prints 0

The sizeof Operator

sizeof tells you how many bytes a type or variable uses in memory:

Example

#include <stdio.h>

int main(void) {
  printf("int: %zu bytes\n", sizeof(int));
  printf("char: %zu byte\n", sizeof(char));
  return 0;
}

Output

int: 4 bytes
char: 1 byte

The size of int can be different on some systems, but 4 bytes is the usual value on modern computers.

Exercise

What is the value of 23 % 4 in C?

535.754