用移位运算符计算出正确的1和0的组合，并将其放入字符串中

Question

#include <stdio.h>
#include <limits.h>
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'; //这里是什么鬼？pa[31]=00010是这样吧？
ps[size] = '\0';
return ps;
}
void show_bstr(const char * str)
{
int i = 0;
while (str[i])
{
putchar(str[i]); //从这里开始就完全看不懂了
if (++i % 4 == 0 && str[i])
putchar(' ');
}
}

Answer 1

01&n是判断最低位是否为1。结果只是0或1，加上'0'是转成字符