Fibonacci Series & prime number in C++

Swap two variables without using third variable

#include
#include

int main()
{
int var1, var2;
 cout<<"enter value for first integer:  ";
 cin>>var1;
 cout<<"enter value for second integer:  ";
 cin>>var2;
 cout<<" values before swapping:  "<  cout<<"first integer ="<  cout<<"second interger ="<
              var1=var1+var2;
              var2=var1-var2;
              var1=var1-var2;
 cout<<" values after swapping:  "<  cout<<"first integer ="<  cout<<"second interger ="<     return 0;

}

Find last prime number occur before enter number

#include
#include

int main()
{
 int num,count=0;
 cout<<"Enter number to find last prime number occurs before it: ";
 cin>>num;
  for( int a=num-1;a>=1;a--)
  {
   for(int b=2;b       {
       if(a%b==0)
       count++;
       }
       if(count==0)
       {
      if(a==1)
       {
       cout<<"no prime number less than 2";
       break;
     }
      cout<        break;
       }
       count=0;
}
return 0;
}

C++ program to find Fibonacci Series upto given range

    #include

    #include

   int main()

    {

       int range, first = 0, second = 1, fibonicci=0;

       cout << "enter range for terms of fibonacci sequence: ";

       cin >> range;

       cout << "fibonicci series upto " << range << " terms "<< endl;

       for ( int c = 0 ; c < range ; c++ )

       {

          if ( c <= 1 )

             fibonicci = c;

          else

          {

             fibonicci = first + second;

             first = second;

             second = fibonicci;

          }

          cout << fibonicci <<" ";

       }

       return 0;

    }

C++ code which take two numbers from user and swap using built in swap function

#include

 #include

void swap()

{

    cout<<"this is my swap";

}

int main()

{

    int firstnum , secondnum;

    cout<<"enter value for first number:   ";

    cin>>firstnum;

    cout<<"enter value for second number:  ";

    cin>>secondnum;

    cout<<"\n\n";

    cout<<"values before calling built in swap function"<

    cout<<"\tfirst  number = "<

    cout<<"\tsecond number = "<

     cout<<"\n\n";

     std::swap( firstnum , secondnum );

    cout<<"values after calling bulit in  swap function"<

    cout<<"\tfirst number = "<

    cout<<"\tsecond number = "<

    return 0;

}