【提问】关于程序里isspace（）和char的问题

#include <stdio.h>
#include <string.h>
#include <ctype.h>
int word (char *);
int main ()
{
char aaa[81];
int a;
puts ("请输入字符串: ");
gets (aaa);
puts ("你输入的第一个单词是: ");
a = word (aaa);
puts (aaa + a);
system ("pause");
return 0;
}
int word (char * str)
{
int a, b;
a = 0;
while (isspace (str[a]))
{
++a;
}
b = a;
while (!isspace (str[b]))
{
++b;
}
str[b] = *\0*;
return a;
}

........upup