#include<stdio.h>
void main()
{
    char c;
    c=getchar();
    if(0<=c&&c<=9);
    printf("this is a digit\n");
    else if('a'<c&&c<'Z')
    printf("this is a small letter\n");
    else if('A'<=c&&c<='Z')
    printf("this is a capital letter\n");
    else
        printf("this is the other\n");



}

if(0<=c&&c<=9);
改成if('0'<=c&&c<='9')去掉分号

#include<stdio.h>
void main()
{
    char c;
    c=getchar();
    if(c>='0'&&c<='9')
    printf("this is a digit%d\n",c);
    else if(c>='a'&&c<'Z')
    printf("this is a small lette%c\n",c);
    else if(c>='A'&&c<='Z')
    printf("this is a capital letter%c\n",c);
    else
        printf("this is the other\n");}
看看

#include<stdio.h>
int main()
{
    char c;
    c=getchar();
    if(c>='0'&&c<='9')//注意c为字符型
    printf("this is a digit\n");
    else if(c>='a'&&c<='z')
    printf("this is a small letter\n");
    else if(c>='A'&&c<='Z')
    printf("this is a capital letter\n");
    else
        printf("this is the other\n");

   return 0;

}

学习了

顶上~~~~~~~LZ应该多看书~~特别一定要搞清楚的是把不要一种数据类型赋予另外一种数据类型的值或者是用另外一种数据类型来限定范围~~都会出现错误~~或者是出现的结果不对~~