Preprocessor Directives in C++ Part – 1

Program 1

/*
  File inclusing 
  Macro statements   # define
  Condition Complition
  Miscellaneous Directive 
*/

#include <iostream>  // File inclusion
using namespace std;
#define SIZE 10  //  # macro
#define output cout
#define input cin

int main()     
{
    system("cls");
     int n;
     output<<"Enter a number";
     input>>n;
     if(n>10)
     cout<<"Hello";
     else
     cout<<"Bye";



     // if(60>10 and 80<20 or 90>10)

    // int sum=0;
    // int ar[SIZE];
    // for(int i=0;i<SIZE;i++)    
    // cin>>ar[i];

    // for(int i=0;i<SIZE;i++)    
    // cout<<ar[i];

    //     for(int i=0;i<SIZE;i++)    
    //     {
    //       cout<<ar[i];
    //       sum=sum+ar[i];
    //     } 
    return 0;
}

Program 2

#include <iostream>
using namespace std;
#define add(a,b) a+b
#define add(a,b) a-b
#define add(a,b) a*b
# define area(r) 3.14*r*r

int main()
{
    system("cls");
    float r,A;
    cout<<"Enter redious";
    cin>>r;
    A=area(r);
    cout<<"Area is : "<<A;
     
    return 0;
}