为什么scanf函数的行为怪异字符的输入？ [英] Why scanf is behaving weird for char input?

问题描述

  / *以下写的宏：1.二没的算术平均值。
2.没有绝对值。
3.要一个大写字母转换为小写。
4.为了获得更大的两个数字。* /＃包括LT＆;＆stdio.h中GT;的#define点（A，B）（（A + B）/ 2）
＃定义ABS（A）（A＆GT; = 0：-a？）
UL的#define（CH）（CH＆GT; = 65安培;＆安培; CH＆LT; = 96 + CH 32：CH）
＃定义较大（A，B）（A＆GT; = B A：B）诠释主（）{    INT X，Y;
    焦炭℃;    的printf（\\ n输入两个数字：）;
            scanf函数（％D，＆安培; X，＆安培; Y）;    输出（两个数\\ n该算术平均值％F，（浮点）上午（X，Y））;    的printf（\\ n输入数字：）;
            scanf函数（％d个，＆安培; X）;    输出（数\\ n该绝对值为％d，ABS（X））;    的printf（\\ n输入的字符：）;
            scanf函数（％C，和C）;    的printf（小写\\ n此信是％C，UL（C））;    的printf（\\ n输入两个数字：）;
            scanf函数（％D，＆安培; X，＆安培; Y）;    的printf（\\ n该更大两个数为％d，更大（X，Y））;
 返回0; }
 

一切正常，只是程序采取字符输入不会停止。

下面是输出的快照....

 输入两个数字：4
  五
  两个数的算术平均值是4.000000  输入号码：-7 ** / *按下回车键在这里它达到线没有了。 7 * / **
  数的绝对值是7  输入字符：
  小写字母是  输入两个数字：4 ** / *号线。 7 * / **
  6  两个数字的更大的是6
 

解决方案

我相信这里的问题是，你的scanf函数（％C，和C）被抓住了回车进入，当你按下回车键放于-7。

将一个getchar函数（或其他scanf函数（％C，和C））。scanf函数之前权利，你不应该有这个问题。

/* Write macro for the following : 

1. Arithmetic Mean of two no.
2. Absolute value of a no.
3. To convert a Uppercase letter to lower case.
4. To obtain bigger of two numbers.

*/

#include<stdio.h>

#define am(a,b) ((a+b)/2)
#define abs(a) (a>=0?a:-a)
#define ul(ch) (ch>=65 && ch<=96 ? ch+32 : ch)
#define bigger(a,b) (a>=b?a:b)

int main () {

    int x,y;
    char c;

    printf("\nEnter two numbers:");
            scanf("%d%d",&x,&y);

    printf("\nThe arithmetic mean of two numbers is %f",(float)am(x,y));

    printf("\nEnter the number:");
            scanf("%d",&x);

    printf("\nThe absolute value of the number is %d",abs(x));

    printf("\nEnter the character:");
            scanf("%c",&c);

    printf("\nThe letter in lower case  is %c",ul(c));

    printf("\nEnter two numbers:");
            scanf("%d%d",&x,&y);

    printf("\nThe bigger of two numbers is %d",bigger(x,y));


 return 0;

 }

Everything is working fine except that program does not stop for taking character input.

Here is the snapshot of the output ....

  Enter two numbers:4
  5
  The arithmetic mean of two numbers is 4.000000

  Enter the number:-7   **/*After hitting enter here it reaches line no. 7 */** 
  The absolute value of the number is 7

  Enter the character:                                          
  The letter in lower case  is  

  Enter two numbers:4   **/*line no. 7*/**
  6

  The bigger of two numbers is 6

解决方案

I believe the problem here is that your scanf("%c",&c) is grabbing the carriage return entered when you hit enter to put in the -7.

Put a getchar (or another scanf("%c",&c)) right before the scanf and you shouldn't have that problem.

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