#include <stdio.h>
int main()
{
    char c;
    int letter=0,space=0,digit=0,other=0;
    printf("请输入一行字符:\n");
    while((c=getchar())!='\n')
    {
        if(c>='a'&&c<='z'||c>='A'&&c<='Z')
            letter++;
        else if(c==' ')
            space++;
        else if(c>='0'&&c<='9')
            digit++;
        else
            other++;
    }
  其中while((c=getchar())!='\n')这一地方我不懂，)!='\n'这是啥意思？