Mine

#include <iostream.h>
#include <stdlib.h>
#include <stdio.h>
#include <math.h>
struct kyklos{
    float aktina;
    }k;
struct tetragwno{
    float pleura;
    }t;
struct orthogwnio{
    float pleura1;
    float pleura2;
    }o;
struct trigwno{
    float mhkos1;
    float mhkos2;
    float mhkos3;
    }tr;

int main()
{
      char x;
      float embado;

      printf ("dwse ena apo ta grammata: K, T, O,R");
      scanf ("%c",x);
      switch (x)
      {
      case 'K':
         scanf ("%f",&k.aktina);
         embado=3.14*pow(k.aktina,2);
         printf ("to embado tou kyklou einai:%f\n",embado);
         break;
      case 'T':
         scanf ("%f",&t.pleura);
         embado=t.pleura*t.pleura;
         printf ("to embado tou tetragwnou einai :%f\n",embado);
         break;
      case 'O':
         scanf ("%f",&o.pleura1);
         scanf ("%f",&o.pleura2);
         embado=o.pleura1*o.pleura2;
         printf ("to embado tou orthogwniou einai :%f\n",embado);
         break;
      case 'R':
         scanf ("%f",&tr.mhkos1);
         scanf ("%s",&tr.mhkos2);
         scanf ("%s",&tr.mhkos3);
         break;
         }
    system("PAUSE");
      return 0;
    }