0 is used with whole and real numbers : printf 0s « printf scanf « C Tutorial

1. C Tutorial
2. printf scanf
3. printf 0s

0 causes 0s to be padded to complete the field width.

If the precision is specified as 0, then this flag is ignored.

if the 0 and - flags are both specified, the 0 flag is ignored.

#include <stdio.h>

main()
{
    printf("%0f", -25.2);
}

-25.200000