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我正在尝试编写一个程序来获取一个字符，然后检查并打印它是大写还是小写。然后我希望它继续循环，直到用户输入应该产生消息的“0”。不起作用的是底部的while条件，条件似乎永远不会满足。

#include <stdio.h>
#include <stdlib.h>

int main()
{
    int ch,nope;    // Int ch and nope variable used to terminate program
    do       // start 'do' loop to keep looping until terminate number is entered
    {
        printf("Enter a character : ");             // asks for user input as a character
        scanf("%c",&ch);                            // stores character entered in variable 'ch'
        if(ch>=97&&ch<=122) {                       // starts if statement using isupper (in built function to check case)
            printf("is lower case\n");
        } else {
            printf("is upper case\n");
        }
    }
    while(ch!=0);                                     // sets condition to break loop ... or in this case print message
    printf("im ending now \n\n\n\n\n",nope);     // shows that you get the terminate line

}
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1 回答 1

2

尝试while(ch!=48);48 是 char '0' 的十进制数。正如 Maroun Maroun 提到的，while(ch!='0'); 更容易理解。

如果您不希望在用户输入“0”时显示大写消息，您可以执行以下操作：

#include <stdio.h>
#include <stdlib.h>

int main()
{
    unsigned char ch,nope;    // Int ch and nope variable used to terminate program
    while (1)
    {
        printf("Enter a character : ");             // asks for user input as a character
        scanf("%c",&ch);                            // stores character entered in variable 'ch'
        if(ch==48) {
            break;
        }
        if(ch>=97&&ch<=122) {                      // starts if statement using isupper (in built function to check case)
            printf("is lower case\n");
        } else {
            printf("is upper case\n");
        }

    }
    printf("im ending now \n\n\n\n\n",nope);     // shows that you get the terminate line

}
于 2013-03-17T21:47:25.207 回答