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Logical Operators in C

Operators in C

In this lesson, we will learn what is the Logical Operators and how it works in C programming with some examples.

What is Logical Operators

Logical operators in C are used to evaluate two or more conditions. They allow a program to make a decision based on multiple conditions. If the result of the logical operator is true then 1 is returned otherwise 0 is returned.

There are 3 types of logical operators in C and they are:

  • && AND
  • || OR
  • ! NOT

Now let's see the examples of all the logical operators one by one for more understanding.

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&& AND Operator

&& (AND) operator is used to check if two or more given conditions are true or not. The output of && (AND) operator is 1 (true) only if all the given conditions are correct otherwise the output will be 0 (false) if any one of the given conditions is wrong.

Example

int x=15, y=2, z=6, k=25, a, b;
a=x>5 && y<6 && k>=25;     // output of a is 1
b=x>y && k<25;             // output of b is 0

In the example above the output of a is 1 because all the three given conditions x>5, y<6 and k>=25 are correct (true). On the other hand the output of b is 0 because out of the two given conditions x>y and k<25 the second condition k<25 is wrong (false).

|| OR Operator

|| (OR) operator is used to check if any one of the given conditions is true or not. The output of || (OR) operator is 1 (true) if at least any one of the given conditions is correct otherwise the output will be 0 (false) only if all the given conditions are wrong.

Example

int x=15, y=2, z=6, k=25, a, b;
a=x<5 || y<6 || k>=25;     // output of a is 1
b=x<y || k<25;             // output of b is 0

In the example above the output of a is 1 because out of the three given conditions x<5, y<6 and k>=25 the second condition is correct (true). On the other hand the output of b is 0 because out of the two given conditions x<y and k<25 both of them are wrong (false).

! NOT Operator

! (NOT) operator negates the value of the condition. If the condition is false then the output of ! (NOT) operator becomes true (1). If the condition is true then the output of ! (NOT) operator becomes false (0).

Example

int x=15, y=10, a, b;
a=!(x>5);     // output of a is 0
b=!(y<5);     // output of b is 1

In the example above the output of a is 0 because the given condition x>5 is correct (true) so ! (NOT) operator changed the output from 1 to 0. On the other hand the output of b is 1 because the given condition y<5 is wrong (false) so ! (NOT) operator changed the output from 0 to 1.

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