#include<stdio.h>
int length(char []);
int main(){
    char val[100];
    printf("please input a string:\n");
    gets(val);
    int num = length(val);
    printf("The string has %d characters.",num);
}
int length(char val[])
{
    int i,sum = 0;
    for(i = 0;val[i] != '\0';i++)
        if(val[i] < '0' && val[i] > '9' && val[i] != ' ')//想去掉数字和空格
            sum++;   
    return sum;
}

if((val[i] < '0' || val[i] > '9') && val[i] != ' ')

感谢

int length(char[]);
int main() {
    char val[100];
    printf("please input a string:\n");
    gets(val);
    int num = length(val);
    printf("The string has %d characters.", num);
    return 0;
}
int length(char val[])
{
    int i,temp, sum = 0;
    for (i = 0; val[i] != '\0'; i++)
    {
        temp = val[i];
        if ((temp>=65&&temp<=90)||(temp>=97&&temp<=122))//对应ASCII码表的大小英文字母
        {
            sum++;
        }
           

    }
       

    return sum;
}

你这个没有标点符号啊，他说只排除空格和数字