Relational Operators in C

Relational operators in C are defined to perform comparison of two values. The familiar angular brackets < and > are the relational operators in addition to a few more as listed in the table below.

These relational operators are used in Boolean expressions. All the relational operators evaluate to either True or False.

C doesn’t have a Boolean data type. Instead, “0” is interpreted as False and any non-zero value is treated as True.

Example 1

Here is a simple example of relational operator in C −

#include <stdio.h>intmain(){int op1 =5;int op2 =3;printf("op1: %d op2: %d op1 < op2: %d\n", op1, op2, op1 < op2);return0;}

Output

Run the code and check its output −

op1: 5 op2: 3 op1 < op2: 0

Relational operators have an important role to play in decision-control and looping statements in C.

The following table lists all the relational operators in C −

Operator	Description	Example
==	Checks if the values of two operands are equal or not. If yes, then the condition becomes true.	(A == B)
!=	Checks if the values of two operands are equal or not. If the values are not equal, then the condition becomes true.	(A != B)
>	Checks if the value of left operand is greater than the value of right operand. If yes, then the condition becomes true.	(A > B)
<	Checks if the value of left operand is less than the value of right operand. If yes, then the condition becomes true.	(A < B)
>=	Checks if the value of left operand is greater than or equal to the value of right operand. If yes, then the condition becomes true.	(A >= B)
<=	Checks if the value of left operand is less than or equal to the value of right operand. If yes, then the condition becomes true.	(A <= B)

All the relational operators are binary operators. Since they perform comparison, they need two operands on either side.

We use the = symbol in C as the assignment operator. So, C uses the “==” (double equal) as the equality operator.

The angular brackets > and < are used as the “greater than” and “less than” operators. When combined with the “=” symbol, they form the “>=” operator for “greater than or equal” and “<=” operator for “less than or equal” comparison.

Finally, the “=” symbol prefixed with “!” (!=) is used as the inequality operator.

Example 2

The following example shows all the relational operators in use.

#include <stdio.h>intmain(){int a =21;int b =10;int c ;printf("a: %d b: %d\n", a,b);if(a == b){printf("Line 1 - a is equal to b\n");}else{printf("Line 1 - a is not equal to b\n");}if(a < b){printf("Line 2 - a is less than b\n");}else{printf("Line 2 - a is not less than b\n");}if(a > b){printf("Line 3 - a is greater than b\n");}else{printf("Line 3 - a is not greater than b \n\n");}/* Lets change value of a and b */
   a =5;
   b =20;printf("a: %d b: %d\n", a,b);if(a <= b){printf("Line 4 - a is either less than or equal to  b\n");}if(b >= a){printf("Line 5 - b is either greater than  or equal to b\n");}if(a != b){printf("Line 6 - a is not equal to b\n");}else{printf("Line 6 - a is equal to b\n");}return0;}

Output

When you run this code, it will produce the following output −

a: 21 b: 10
Line 1 - a is not equal to b
Line 2 - a is not less than b
Line 3 - a is greater than b

a: 5 b: 20
Line 4 - a is either less than or equal to  b
Line 5 - b is either greater than  or equal to b
Line 6 - a is not equal to b

Example 3

The == operator needs to be used with care. Remember that “=” is the assignment operator in C. If used by mistake in place of the equality operator, you get an incorrect output as follows −

#include <stdio.h>intmain(){int a =5;int b =3;if(a = b){printf("a is equal to b");}else{printf("a is not equal to b");}return0;}

Output

The value of “b” is assigned to “a” which is non-zero, and hence the if expression returns true.

a is equal to b

Example 4

We can have “char” types too as the operand for all the relational operators, as the “char” type is a subset of “int” type. Take a look at this example −

#include <stdio.h>intmain(){char a ='B';char b ='d';printf("a: %c b: %c\n", a,b);if(a == b){printf("Line 1 - a is equal to b \n");}else{printf("Line 1 - a is not equal to b \n");}if(a < b){printf("Line 2 - a is less than b \n");}else{printf("Line 2 - a is not less than b \n");}if(a > b){printf("Line 3 - a is greater than b \n");}else{printf("Line 3 - a is not greater than b \n");}if(a != b){printf("Line 4 - a is not equal to b \n");}else{printf("Line 4 - a is equal to b \n");}return0;}

Output

Run the code and check its output −

a: B b: d
Line 1 - a is not equal to b
Line 2 - a is less than b
Line 3 - a is not greater than b
Line 4 - a is not equal to b

Relational operators cannot be used for comparing secondary types such as arrays or derived types such as struct or union types.