In order to evaluate a comparison between two expressions, a relational operator can be used. The result of a relational operation is a Boolean
value that can only be true
or false
.
In C++, there are six relational operators. They include:
==
!=
>
<
>=
<=
They are called relational because they evaluate how two expressions on either side of the operator relate to each other.
For example, the relation $5>10$ produces the integer value 0
, meaning false
.
The descriptions, as well as examples of the six relational operators, are represented in the table below. Assume variable A
holds 1
and variable B
holds 2
, then:
Operator | Description | Example |
== | Helps check if the values of two operand are equal or not, if they are equal then condition becomes true | A == B is not true because A is not equal to B |
!= | Helps check if the values of two operands are equal or not, if the values are not equal then condition becomes true | A != B is true because A and B are not equal |
> | Helps check if the value of left operand is greater than the value of right operand, if A is greater than B, then condition becomes true | A > B is not true because A is not greater than B |
< | Helps check if the value of left operand is less than the value of right operand, if A is less than B, then the condition becomes true | A < B is true because A is less than B |
>= | Helps check if the value of left operand is greater than or equal to the value of right operand, if the value of A is either greater or equal to the value of B, then the condition becomes true | A >= B is not true because A is neither greater nor equal to B |
<= | Helps check if the value of left operand is less than or equal to the value of right operand, if A is either less or equal to B, then the condition becomes true | A <= B is true because A is at least greater than B |
Now, let’s see a very simple example using the relational operator greater than >
.
#include <iostream> using namespace std; int main() { int x,y; cout<<"Enter two integers:"; cin>>x>>y; if(x>y)cout<<x<<endl; else cout<<y<<endl; return 0; }
Enter two integers: 10, 20
20
In the program above, the condition given is (x>y)
. If x
is greater than y
, the condition is true
and evaluates to 1; otherwise, the condition is false
and evaluates to 0. So, x
is printed precisely when it is greater than y
.
Below, the example includes all relational operators in the example below.
In the code below, $a = 2$ and $b = 1$.
#include <iostream> using namespace std; int main() { int a=2; int b=1; if(a==b) { cout << "Line 1: a is equal to b"<<endl; } else { cout << "Line 1: a is not equal to b"<<endl; } if(a<b) { cout << "Line 2: a is less than b"<<endl; } else { cout << "Line 2: a is not less than b"<<endl; } if(a>b) { cout << "Line 3: a is greater than b"<<endl; } else { cout << "Line 3: a is not greater than b"<<endl; } /* lets change the values of a and b */ a=5; b=20; if(a<=b) { cout << "Line 4: a is either less than or equal to b"<<endl; } if(b>=a) { cout << "Line 5: a is not greater than or equal to b"<<endl; } return 0; }
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