An operator is a symbol that operates on a value or a variable. For example: + is an operator to perform addition.

C has a wide range of operators to perform various operations.

C Arithmetic Operators

An arithmetic operator performs mathematical operations such as addition, subtraction, multiplication, division etc on numerical values (constants and variables).

Example 1: Arithmetic Operators

// Working of arithmetic operators
#include <stdio.h>
int main(){
    int a = 9,b = 4, c;
    
    c = a+b;
    printf("a+b = %d n",c);
    c = a-b;
    printf("a-b = %d n",c);
    c = a*b;
    printf("a*b = %d n",c);
    c = a/b;
    printf("a/b = %d n",c);
    c = a%b;
    printf("Remainder when a divided by b = %d n",c);
    
    return 0;
}

Output

a+b = 13
a-b = 5
a*b = 36
a/b = 2
Remainder when a divided by b=1

The operators +, - and * computes addition, subtraction, and multiplication respectively as you might have expected.

In normal calculation, 9/4 = 2.25. However, the output is 2 in the program.

It is because both the variables a and b are integers. Hence, the output is also an integer. The compiler neglects the term after the decimal point and shows answer 2 instead of 2.25.

The modulo operator % computes the remainder. When a=9 is divided by b=4, the remainder is 1. The % operator can only be used with integers.

Suppose a = 5.0, b = 2.0, c = 5 and d = 2. Then in C programming,

// Either one of the operands is a floating-point number
a/b = 2.5  
a/d = 2.5  
c/b = 2.5  

// Both operands are integers
c/d = 2

C Increment and Decrement Operators

C programming has two operators increment ++ and decrement -- to change the value of an operand (constant or variable) by 1.

Increment ++ increases the value by 1 whereas decrement -- decreases the value by 1. These two operators are unary operators, meaning they only operate on a single operand.

Example 2: Increment and Decrement Operators

// Working of increment and decrement operators
#include <stdio.h>
int main(){
    int a = 10, b = 100;
    float c = 10.5, d = 100.5;

    printf("++a = %d n", ++a);
    printf("--b = %d n", --b);
    printf("++c = %f n", ++c);
    printf("--d = %f n", --d);

    return 0;
}

Output

++a = 11
--b = 99
++c = 11.500000
++d = 99.500000

Here, the operators ++ and -- are used as prefixes. These two operators can also be used as postfixes like a++ and a--. Visit this page to learn more about how increment and decrement operators work when used as postfix.

C Assignment Operators

An assignment operator is used for assigning a value to a variable. The most common assignment operator is =

Example 3: Assignment Operators

// Working of assignment operators
#include <stdio.h>
int main(){
    int a = 5, c;

    c = a;      // c is 5
    printf("c = %dn", c);
    c += a;     // c is 10 
    printf("c = %dn", c);
    c -= a;     // c is 5
    printf("c = %dn", c);
    c *= a;     // c is 25
    printf("c = %dn", c);
    c /= a;     // c is 5
    printf("c = %dn", c);
    c %= a;     // c = 0
    printf("c = %dn", c);

    return 0;
}

Output

c = 5 
c = 10 
c = 5 
c = 25 
c = 5 
c = 0

C Relational Operators

A relational operator checks the relationship between two operands. If the relation is true, it returns 1; if the relation is false, it returns value 0.

Relational operators are used in decision making and loops.

Example 4: Relational Operators

// Working of relational operators
#include <stdio.h>
int main(){
    int a = 5, b = 5, c = 10;

    printf("%d == %d is %d n", a, b, a == b);
    printf("%d == %d is %d n", a, c, a == c);
    printf("%d > %d is %d n", a, b, a > b);
    printf("%d > %d is %d n", a, c, a > c);
    printf("%d < %d is %d n", a, b, a < b);
    printf("%d < %d is %d n", a, c, a < c);
    printf("%d != %d is %d n", a, b, a != b);
    printf("%d != %d is %d n", a, c, a != c);
    printf("%d >= %d is %d n", a, b, a >= b);
    printf("%d >= %d is %d n", a, c, a >= c);
    printf("%d <= %d is %d n", a, b, a <= b);
    printf("%d <= %d is %d n", a, c, a <= c);

    return 0;
}

Output

5 == 5 is 1
5 == 10 is 0
5 > 5 is 0
5 > 10 is 0
5 < 5 is 0
5 < 10 is 1
5 != 5 is 0
5 != 10 is 1
5 >= 5 is 1
5 >= 10 is 0
5 <= 5 is 1
5 <= 10 is 1 

C Logical Operators

An expression containing logical operator returns either 0 or 1 depending upon whether expression results true or false. Logical operators are commonly used in decision making in C programming.

Example 5: Logical Operators

// Working of logical operators

#include <stdio.h>
int main(){
    int a = 5, b = 5, c = 10, result;

    result = (a == b) && (c > b);
    printf("(a == b) && (c > b) is %d n", result);
    result = (a == b) && (c < b);
    printf("(a == b) && (c < b) is %d n", result);
    result = (a == b) || (c < b);
    printf("(a == b) || (c < b) is %d n", result);
    result = (a != b) || (c < b);
    printf("(a != b) || (c < b) is %d n", result);
    result = !(a != b);
    printf("!(a == b) is %d n", result);
    result = !(a == b);
    printf("!(a == b) is %d n", result);

    return 0;
}

Output

(a == b) && (c > b) is 1 
(a == b) && (c < b) is 0 
(a == b) || (c < b) is 1 
(a != b) || (c < b) is 0 
!(a != b) is 1 
!(a == b) is 0 

Explanation of logical operator program

• (a == b) && (c > 5) evaluates to 1 because both operands (a == b) and (c > b) is 1 (true).
• (a == b) && (c < b) evaluates to 0 because operand (c < b) is 0 (false).
• (a == b) || (c < b) evaluates to 1 because (a = b) is 1 (true).
• (a != b) || (c < b) evaluates to 0 because both operand (a != b) and (c < b) are 0 (false).
• !(a != b) evaluates to 1 because operand (a != b) is 0 (false). Hence, !(a != b) is 1 (true).
• !(a == b) evaluates to 0 because (a == b) is 1 (true). Hence, !(a == b) is 0 (false).

C Bitwise Operators

During computation, mathematical operations like: addition, subtraction, multiplication, division, etc are converted to bit-level which makes processing faster and saves power.

Bitwise operators are used in C programming to perform bit-level operations.

Other Operators

Comma Operator

Comma operators are used to link related expressions together. For example:

int a, c = 5, d;

The sizeof operator

The sizeof is a unary operator that returns the size of data (constants, variables, array, structure, etc).

Example 6: sizeof Operator

#include <stdio.h>
int main(){
    int a;
    float b;
    double c;
    char d;
    printf("Size of int=%lu bytesn",sizeof(a));
    printf("Size of float=%lu bytesn",sizeof(b));
    printf("Size of double=%lu bytesn",sizeof(c));
    printf("Size of char=%lu byten",sizeof(d));

    return 0;
}

Output

Size of int = 4 bytes
Size of float = 4 bytes
Size of double = 8 bytes
Size of char = 1 byte

Other operators such as ternary operator ?:, reference operator &, dereference operator * and member selection operator -> will be discussed in later tutorials.