l1_4_3.cpp

这是我自己写的并参考的一部分C++primer的程序

#include <iostream.h>
#include <stdio.h>
#include <stdlib.h>

void main()
{  
   int v1,v2;
   int lower,upper; 
   cout<<"Enter two numbers: ";
   cin>>v1>>v2;
   if(v1<=v2)
      {
        lower=v1;
        upper=v2;
   }else{
         lower=v2;
         upper=v1;
   }
   int sum=0;
   for(int val=lower;val<=upper;val++)
       {
        sum+=val;
       }
       cout<<"sum of "<<lower<<" to "
            <<upper<<" is "<<sum;
       getchar();
       getchar();
}