Answer:
<em>The programming language is not stated;</em>
<em>I'll answer using C++</em>
#include<iostream>
#include<cmath>
using namespace std;
int main()
{
 int side1, side2, side3;
 cout<<"Enter the three sides of the triangle: "<<endl;
 cin>>side1>>side2>>side3;
 if(side1<=0 || side2 <= 0 || side3 <= 0)
{
  cout<<"Invalid Inputs";
 }
 else
{
  if(abs(pow(side1,2) - (pow(side2,2) + pow(side3, 2)))<0.001)
{
  	cout<<"Right Angled";
  }
  else if(abs(pow(side2,2) - (pow(side1,2) + pow(side3, 2)))<0.001)
{
  	cout<<"Right Angled";
  }
  else if(abs(pow(side3,2) - (pow(side2,2) + pow(side1, 2)))<0.001)
{
  	cout<<"Right Angled";
  }
  else
{
  	cout<<"Not Right Angled";
  }
 }
 return 0;
}
Explanation:
The following line declares the three variables
 int side1, side2, side3;
The next line prompts user for input of the three sides
 cout<<"Enter the three sides of the triangle: "<<endl;
The next line gets user input
 cin>>side1>>side2>>side3;
The following if condition checks if any of user input is negative or 0
<em> if(side1<=0 || side2 <= 0 || side3 <= 0)
{
</em>
<em>  cout<<"Invalid Inputs";
</em>
<em> }
</em>
If otherwise
 else
{
The following if condition assumes that side1 is the largest and test using Pythagoras Theorem
<em>if(abs(pow(side1,2) - (pow(side2,2) + pow(side3, 2)))<0.001)
{
</em>
<em>  	cout<<"Right Angled";
</em>
<em>  }
</em>
The following if condition assumes that side2 is the largest and test using Pythagoras Theorem
<em>  else if(abs(pow(side2,2) - (pow(side1,2) + pow(side3, 2)))<0.001)
{
</em>
<em>  	cout<<"Right Angled";
</em>
<em>  }
</em>
The following if condition assumes that side3 is the largest and test using Pythagoras Theorem
<em>  else if(abs(pow(side3,2) - (pow(side2,2) + pow(side1, 2)))<0.001)
{
</em>
<em>  	cout<<"Right Angled";
</em>
<em>  }
</em>
If none of the above conditions is true, then the triangle is not a right angles triangle
<em>  else
{
</em>
<em>  	cout<<"Not Right Angled";
</em>
<em>  }
</em>
 }
 return 0;