C :

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<math.h>
int main()
{
	int j=0,o=0,i;
	for(i=1;i<=100;i++)
	{
		if(i%2==1)j=j+i;
			else o=o+i;
		}
		printf("the sum of  odd  numbers  1 to 100 is : %d\n",j);
		printf("the sum of  even  numbers  1 to 100 is : %d",o);
return 0;
}

C++ :

#include<iostream>
using namespace std;
int main()
{
  int a=0,b=0;
  for (int x=1,y=2;x<=99&&y<=100;x=x+2,y=y+2)
  { a=a+x;b=b+y;
  }
  cout<<"the sum of  odd  numbers  1 to 100 is : "<<a<<endl;
  cout<<"the sum of  even  numbers  1 to 100 is : "<<b<<endl;
  return 0;
}