C程序：使用标准输入scanf函数读取字符时出错 [英] C Program :Error when reading character from stdin using scanf

问题描述

目前我试着去学习简单的C程序。但是，我来到了这个情况：

Currently im trying to learn simple C Programs. But, i came into this situation :

#include<conio.h>
#include<stdio.h>

void main()
{
   char c;
   int tryagain=1;

   while(tryagain>0){
       printf("Enter the Character : ");
   scanf("%c",&c);
       printf("You entered the character \"%c\" and the ascii value is %d",c,c);

    getch();
    clrscr();
    tryagain=0;

    printf("You want to Trry again Press 1 : ");
    scanf("%d",&tryagain);
    clrscr();

    }
 }

该计划是好的，当用户第一次输入的字符。并且，当它要求继续。而且，用户输入1那么它的行为weired。它会自动输入空白字符和打印的ASCII和GOTO一样的地方。

The program is fine when user first enter a character. And, when it ask to continue. And, user enter 1 then it is behaving weired. It automatically input blank character and prints the ascii and goto the same place.

我该如何解决？而且，特别是，为什么这样做的原因？

How can i resolve this? And, specially, Why is the reason for this?

和，对不起我的英语不好！

And, Im sorry about my poor english!

感谢您提前。

推荐答案

的问题是，你正在阅读的第二个scanf的单号，但用户输入的多单数出现，用户还输入了新行字符由pressing。

The issue is that you are reading a single number in the second scanf, but user inputs more than a single number there, the user also input a new line character by pressing .

用户输入1 \\ N。您的scanf的读1，而忽略了\\ n个输入流。那么接下来scanf函数读取字符从流中读取\\ n。

User enters "1\n". Your scanf reads "1", leaving out "\n" in the input stream. Then the next scanf that reads a character reads "\n" from the stream.

下面是更正后的code。我用的getc放弃额外的新行字符是存在的。

Here is the corrected code. I use getc to discard the extra new line character that is there.

#include <stdio.h>

void main()
{
    char c;
    int tryagain = 1;

    while (tryagain > 0) {
        printf("Enter a character: ");
        scanf("%c", &c);
        printf("You entered the character \"%c\" and the ascii value is %d\n", c, c);

        tryagain = 0;

        printf("If you want to try again, enter 1: ");
        scanf("%d", &tryagain);
        // get rid of the extra new line character
        getc(stdin);
    }
}

---

此外，作为一个侧面说明，您可以使用 CONIO.H 这不是标准C的一部分，它是MS-DOS的头文件，因此它不是可移植的C你是写作。我从code删除它，但你可能希望保留它。

---

Also, as a side note, you use conio.h which is not part of standard C, it's MS-DOS header file, thus it's not portable C you are writing. I have removed it from my code, but you might wish to keep it.

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