casting in c

#include <stdio.h>

main() {

   int sum = 17, count = 5;
   double mean;

   mean = (double) sum / count;
   printf("Value of mean : %f\n", mean );
}
#include <stdio.h>
#include <stdlib.h>
int main(){
  int x = 7, y = 5;
  float z;
  z = (float)x / (float)y;   /*Here the value of z is 1.400000*/
  return 0;
}(new_type) name_var;