c语言中将一个十进制数按照二进制输出

c语言中将一个十进制数按照二进制输出

1、

#include <stdio.h>

int main(void)
{
    int bits = 0;
    unsigned tmp = ~0U;
    while(tmp)
    {
        if(tmp & 1U)
            bits++;
        tmp >>= 1;
    }
    
    int i;
    unsigned x;
    puts("please input a decimal number.");
    printf("x = "); scanf("%u", &x);
    
    for(i = bits - 1; i >= 0; i--)
    {
        putchar(x >> i & 1U ? '1' : '0');
    }
    putchar('\n');
    
    return 0;
}

 

2、

#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_bits(unsigned x)
{
    int i;
    for(i = int_bits() - 1; i >= 0; i--)
    {
        putchar((x >> i & 1U) ? '1' : '0');  
    }
    putchar('\n');
}

int main(void)
{
    unsigned a;
    puts("please input a decimal number.");
    printf("a = "); scanf("%u", &a);
    
    printf("\nbinary a          = "); print_bits(a);
    return 0;
}

 

 

3、

#include <stdio.h>

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

int print_bits(unsigned x)
{
    int i;
    for(i = count_bits() - 1; i >= 0; i--)
    {
        putchar((x >> i & 1U) ? '1' : '0');
    }
    putchar('\n');
}

int main(void)
{
    unsigned a;
    puts("please input an decimal number.");
    printf("a = "); scanf("%u", &a);
    
    printf("\nbinary a     = ");  print_bits(a);
    return 0;
}