程序代码：

#include<stdio.h>
main(void)
{
char c;
int letters=0,space=0,digit=0,others=0;
printf("请输入一行字符"); 
while((c=getchar())!='\n')
{
   if(c>='a'&&c<='z'||c>='A'&&c<='Z')
    letters ++;
    else if(c>='0'&&c<='9')
       digit ++;
    else if(c==' ')
       space ++;
    else
        others ++;
  }
printf("char=%d,space=%d,digit=%d,others=%d\n",letters,space,digit,others); 
}