为什么这段代码无法正常工作？ [英] Why this code not working s expected?

问题描述

我写了一个小代码，手动接收输入并在屏幕上显示，目的是如果我们输入'a'的字符串只有一个'a'应该在屏幕上打印并且应该跳过休息。

I have written a small code, which takes input manually and display on screen, aim was if we enter string of 'a' only one 'a' should be printed on screen and rest should be skipped.

<pre>int main()
{
    int c, count=0;
    while((c=getchar())!=EOF)
    {
        if(c=='a' && count==0)
        {
            count++;
            printf("%c",c);
        }
        if(c!='a')
        {
            count=0;
            printf("%c",c);
        }

    }
    return 0;
}

我的尝试：



但是我每次都会打印出来，任何人都可以帮忙。

What I have tried:

But i am getting a printed every-time, can anyone help on this.

推荐答案

getchar（）从 stdin 流中读取缓冲输入，并在控制台上回显输入的字符。键入字符时，您在程序中看到的是回显字符。



按 ENTER 键后， getchar（）返回直到读取所有缓冲输入。



自己尝试一下：

getchar() reads buffered input from the stdin stream and echoes the entered character on the console. What you are seeing with your program when typing characters are the echoed characters.

Once you press the ENTER key, getchar() returns until all buffered input is read.

Try it out yourself:

aaacba[RETURN]
acba

您可能需要的是读取没有回声和缓冲输入的字符。使用Windows时，请使用 _getch，_getwch [ ^ ]代替：

What you probably need is reading characters without echo and buffered input. When using Windows, use _getch, _getwch[^] instead:

while(1)
{
    c = _getch();
    // Must defined a character to quit the application
    if (c == 'Q')
        break;
    // ...
}

使用Linux，您必须使用 termios 或像这样的库ncurses 。

看起来它应该有效，所以你需要先检查一下。

首先，再次编译你的代码。有没有错误或警告？如果是这样，那么将不会生成新的EXE文件，因此您运行的代码可能不是您向我们展示的代码。



当您没有错误或警告，但仍然有同样的问题，你将不得不使用调试器找出问题所在。



编译并不意味着你的代码是正确的！ ：笑：

将开发过程想象成编写电子邮件：成功编译意味着您使用正确的语言编写电子邮件 - 例如英语而不是德语 - 而不是电子邮件包含您的邮件想发送。



所以现在你进入第二阶段的发展（实际上它是第四或第五阶段，但你将在之后的阶段进入）：测试和调试。



首先查看它的作用，以及它与你想要的有何不同。这很重要，因为它可以为您提供有关其原因的信息。例如，如果程序旨在让用户输入一个数字并将其翻倍并打印答案，那么如果输入/输出是这样的：

That looks like it should work, so you need to start by checking some things.
First, compile your code again. Were there any errors or warnings? If so, then a new EXE file will not be generated, so the code you are running may not be the code you show us.

When you get no errors or warnings but still have the same problem, you are going to have to use the debugger to find out what the problem might be.

Compiling does not mean your code is right! :laugh:
Think of the development process as writing an email: compiling successfully means that you wrote the email in the right language - English, rather than German for example - not that the email contained the message you wanted to send.

So now you enter the second stage of development (in reality it's the fourth or fifth, but you'll come to the earlier stages later): Testing and Debugging.

Start by looking at what it does do, and how that differs from what you wanted. This is important, because it give you information as to why it's doing it. For example, if a program is intended to let the user enter a number and it doubles it and prints the answer, then if the input / output was like this:

Input   Expected output    Actual output
  1            2                 1
  2            4                 4
  3            6                 9
  4            8                16

然后很明显问题出在将它加倍的位 - 它不会将自身加到自身上，或者将它乘以2，它会将它自身相乘并返回输入的平方。

所以，你可以查看代码和很明显，它在某处：

Then it's fairly obvious that the problem is with the bit which doubles it - it's not adding itself to itself, or multiplying it by 2, it's multiplying it by itself and returning the square of the input.
So with that, you can look at the code and it's obvious that it's somewhere here:

int Double(int value)
   {
   return value * value;
   }

一旦你知道可能出现的问题，就开始使用调试器找出原因。在你的行上设一个断点：

Once you have an idea what might be going wrong, start using the debugger to find out why. Put a breakpoint on your line:

while((c=getchar())!=EOF)

并运行你的应用程序。在执行代码之前，请考虑代码中的每一行应该做什么，并将其与使用Step over按钮依次执行每一行时实际执行的操作进行比较。它符合您的期望吗？如果是这样，请转到下一行。

如果没有，为什么不呢？它有什么不同？

如果你有这个，你要么已经发现了问题，要么有可靠的信息转发给我们。



这是一项技能，它是值得开发的技能，因为它可以帮助你在现实世界和发展中。和所有技能一样，它只能通过使用来改进！

and run your app. Think about what each line in the code should do before you execute it, and compare that to what it actually did when you use the "Step over" button to execute each line in turn. Did it do what you expect? If so, move on to the next line.
If not, why not? How does it differ?
When you have that, you will either have spotted the problem, or will have solid information to relay back to us.

This is a skill, and it's one which is well worth developing as it helps you in the real world as well as in development. And like all skills, it only improves by use!

键入^ Z（Ctrl + Z）在Windows控制台中可以正常工作，即这被识别为EOF。

Typing ^Z (Ctrl+Z) does work in windows console i.e. this is recognized as EOF.

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