c语言中使用十进制、二进制、八进制和十六进制输出0到65535的整数。

#include <stdio.h>

int count_bits(unsigned x)
{
    int bits = 0;
    while(x)
    {
        if(x & 1U)
            bits++;
        x >>= 1;
    }
    return bits;
}

int int_bits(void)
{
    return count_bits(~0U);
}

int print_nbits(unsigned x, unsigned n)
{
    int i = int_bits();
    i = (n < i) ? n - 1 : i - 1;
    for(; i >= 0; i--)
    {
        putchar((x >> i & 1U) ? ‘1‘ : ‘0‘);
    }
}

int main(void)
{
    unsigned i;
    for(i = 0; i <= 65535U; i++)
    {
        printf("%5u ", i);
        print_nbits(i, 16);
        printf(" %06o %04X\n",i, i); 
    }
    return 0;
}