c 十进制转化为二进制 位操作

#include 
#include 
char *itobs(int, char *);

void show_bstr(const char *);

int main(void)
{
    char bin_str[CHAR_BIT * sizeof(int) + 1];
    int number;

    puts("Enter integers and see them in binary.");
    puts("Non-numeric input terminates program");
    while(scanf("%d", &number) == 1)
    {
        itobs(number, bin_str);
        printf("%d is ", number);
        show_bstr(bin_str);
        putchar('\n');
    }
    puts("Bye!");

    return 0;
}

char *itobs(int n, char *ps)
{
    int i;
    const static int size = CHAR_BIT * sizeof(int);
    for(i = size - 1; i >= 0; i--, n >>= 1)
    {
        ps[i] = (01 & n) + '0';
    }
    ps[size] = '\0';

    return ps;
}

void show_bstr(const char *str)
{
    int i = 0;
    while(str[i])
    {
        putchar(str[i]);
        if(++i % 4 == 0 && str[i])
        {
            putchar(' ');
        }
    }
}