cf. 형변환, 곱셈, 나눗셈

#include <stdio.h>
int main(void)
{
 int x = 10;

 printf("%d\n", x * 10);

 printf("%d\n", x * 10.0);

 printf("%d\n", x / 10);

 printf("%d\n", 5/2);

 printf("%f\n", 5/2);

 printf("%f\n\n", 5.0 / 2);

 printf("%f\n", (double)(x / 2));     // int / int --> int
 printf("%f\n", 5.0 / 2);                 // double / int --> double
 printf("%f\n", 5 / 2.0);                 // int / double --> double
 printf("%f\n", (double)5 / 2);        // double / int --> double
 printf("%f\n", (double)x / 2);        // double / int --> double
 printf("%f\n", x / (double)2);        // int / double --> double
 printf("%f\n", (double)(x / 2));     // double

 return 0;

}

-------------------------------

100
0
1
2
0.000000
2.500000

2
2.500000
2.500000
2.500000
5.000000
5.000000
5.000000

(visual studio 2017)