// m specifies how many of the low bits are shown.
// Replace m with sizeof(n) below for all bits and
// remove it from the parameter list if you like.

void print_binary(unsigned long n, unsigned long m) {
    static char show[3] = "01";
    unsigned long mask = 1ULL << (m-1);
    while(mask) {
        putchar(show[!!(n&mask)]); mask >>= 1;
    }
    putchar('\n');
}

void print_bits (uintmax_t n)
{
    for (size_t i = 8 * sizeof (int); i-- != 0;)
    {
        char c;
        if ((n & (1UL << i)) != 0)
            c = '1';
        else
            c = '0';

        printf ("%c", c);

    }
}

这不是一个覆盖所有地方的解决方案，但如果你想要一些快速、容易理解的东西，我很惊讶还没有人提出这个解决方案。

void print_ulong_bin(const unsigned long * const var, int bits) {
        int i;

        #if defined(__LP64__) || defined(_LP64)
                if( (bits > 64) || (bits <= 0) )
        #else
                if( (bits > 32) || (bits <= 0) )
        #endif
                return;

        for(i = 0; i < bits; i++) { 
                printf("%lu", (*var >> (bits - 1 - i)) & 0x01);
        }
}

应该工作-未经测试。

至于我，我为此编写了一些通用代码

#include<stdio.h>
void int2bin(int n, int* bin, int* bin_size, const int  bits);

int main()
{
    char ch;
    ch = 'A';
    int binary[32];
    int binary_size = 0;
    
    int2bin(1324, binary, &binary_size, 32);
    for (int i = 0; i < 32; i++)
    {
        printf("%d  ", binary[i]);
    }
    
    
    return 0;
}

void int2bin(int n, int* bin,int *bin_size,const int  bits)
{
    int i = 0;
    int temp[64];
    for (int j = 0; j < 64; j++)
    {
        temp[j] = 0;
    }
    for (int l = 0; l < bits; l++)
    {
        bin[l] = 0;
    }

    while (n > 0)
    {
        temp[i] = n % 2;
        n = n / 2;
        i++;
    }
    *bin_size = i;

    //reverse modulus values
    for (int k = 0; k < *bin_size; k++)
    {
        bin[bits-*bin_size+k] = temp[*bin_size - 1 - k];
    }
}

下面是一个不受重入性问题或参数大小/类型限制的函数版本:

#define FMT_BUF_SIZE (CHAR_BIT*sizeof(uintmax_t)+1)

char *binary_fmt(uintmax_t x, char buf[static FMT_BUF_SIZE])
{
    char *s = buf + FMT_BUF_SIZE;
    *--s = 0;
    if (!x) *--s = '0';
    for (; x; x /= 2) *--s = '0' + x%2;
    return s;
}

请注意，这段代码适用于2到10之间的任何底数，只要将2替换为所需的底数。用法是:

char tmp[FMT_BUF_SIZE];
printf("%s\n", binary_fmt(x, tmp));

其中x是任意的积分表达式。

我优化了顶部的解决方案的大小和c++ -ness，并得到了这个解决方案:

inline std::string format_binary(unsigned int x)
{
    static char b[33];
    b[32] = '\0';

    for (int z = 0; z < 32; z++) {
        b[31-z] = ((x>>z) & 0x1) ? '1' : '0';
    }

    return b;
}