在 linux ctrl + d（EOF） 行为中三种不同情况下

问：

//first example
void readInWBW()
{
    int ch; 
    while((ch=getchar()) != EOF)
        putchar(ch);
}

当我输入“qweCTRL+D”时，第一次输入 ctrl+z 只需刷新缓冲区，然后重新输入 “ctrl+d”，所以就像“qweCTRL+DCTRL+D”，然后EOF工作，程序终止。 结果是

$ ./a.out
qweqwe$

//second example
void guess()
{
    int guess = 1;  
    printf("Pick an integer from 1 to 100. I will try to guess ");
    printf("it.\nRespond with a y if my guess is right and with");
    printf("\nan n if it is wrong.\n");
    printf("Uh...is your number %d?\n", guess);
    while (getchar() != 'y'){      //<---------------------------
        printf("Well, then, is it %d?\n", ++guess); //<----------
        sleep(1);
    }
    printf("I knew I could do it!\n");
}

在这个例子中，我输入“qweCTRL+D”，它会显示三次“好吧，那么......”，但如果我再次输入CTRL+D，程序将进入无限循环。 ReusLT 是：

Pick an integer from 1 to 100. I will try to guess it.
Respond with a y if my guess is right and with
an n if it is wrong.
Uh...is your number 1?
qweWell, then, is it 2? //<--------------------------
Well, then, is it 3?
Well, then, is it 4?
Well, then, is it 5?
Well, then, is it 6?
Well, then, is it 7?
Well, then, is it 8?
Well, then, is it 9?
Well, then, is it 10?
Well, then, is it 11?
^C

//third example    
void test()
{
    char ch;
    while((ch = getchar()) != '#')
        putchar(ch); 
}

我尝试像其他示例一样输入“qweCTRL+D”，但是在刷新缓冲区之后，“CTRL+D”不再响应，即使我输入“#”，它仍然没有终止。 结果是：

$ ./a.out
qweqwe
#
#
^C
$

我不明白为什么在 example2 和 example3 中具有无限循环并且无法终止程序。谁能解释一下，谢谢。