Operators in C Language | Part-3

Relational Operator

Relational operators are used to perform a logical test or create a condition. List of the logical operator is as given below...

Relational opertor Meaning
> Greater Than
< Less Than
>= Greater Than or Equal to
<= Less Than or Equal to
== Equal to
!= Not euqal
  1. Every relational operator returns true or false.
  2. In C any non-zero is treated as true and zero is treated as false.
  3. In C if any expression evaluated true then system returns 1 otherwise return 0.
  4. Relational operator are evaluated from left to right.

Example-1


printf("%d",5>2); //print 1

Example-2


printf("%d",5>2>1); //print 0
//first 5>2 evaluated true and returns 1 and then result of this expression is compared with next 1, that is evaluated false.

Logical Operator

  1. &&(And) ||(Or) !(not) are the 3 logical operators.
  2. &&(and), || (or) are used to combine two or more conditions.
  3. Each condition can be true or false, so what will be the output of the combination made by logical operator &&(and) , ||(or). This is decided by truth table.
  4. truth table is the combination of conditionsa and their results as shown below...
C1 C2 C1 && C2 C1 || C2
F F F F
F T F T
T F F T
T T T T

Examples of Relational Operator


int a = 5, b = 6, c;
c = a > 2 && b > 3;
printf("%d %d %d",a,b,c);//5 6 1 


int a = 5 , b = 6, c;
c = a > 2 || b < 8;
printf("%d %d %d",a,b,c);//5 6 1 


printf("%d",5 && 6);//1

//In c any non-zero is treated as true. because 5 and 6 are non-zero so both are true,so the result is true that is 1. 


int a = 5, b = 6, c;
c = a > 2 || ++b;
printf("%d %d %d",a,b,c);//5 6 1

Logical operator are short circuit operator means or(||) operator returns true as soon as if first condtion is true, and(&&) operator returns false as soon as first condition is evaluated false.

Not operator

  1. Not operator just negates the result as the following truth table shown...
C !C
F T
T F

Example of not operator


int a = 5, b;
b = !a > 2;
printf("%d %d",a,b);// 5 0 

//(not) have the greater precedence then (>). so first the !a is evaluated and results 0. After than 0>2 is evaluated that is false.


int a = 5, b;
b = !(a > 2);
printf("%d %d",a,b);// 5 0 

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