c语言中只读取输入的一行字符的首个字符

测试程序1：

#include <stdio.h>

int main(void)
{
    char ch;
    
    printf("please input an character: 
");
    
    while((ch = getchar()) != '#')
        printf("xxx
");
        
    return 0; 
}

测试程序2

#include <stdio.h>

int main(void)
{
    char ch;
    
    printf("please input an character: 
");
    
    while((ch = getchar()) != '#')
    {
        printf("xxx
");
        while(ch = getchar() != '
')    // 为什么起作用？？？？？
            continue;
    }
        
    return 0; 
}