读入一个单词，为什么输入“ 和ctrl+z”时，没有直接退出程序

#include <stdio.h>
#define LEN 80
char * getword(char * str);
int main(void)
{
 char input[LEN];

 while (getword(input) != NULL)
 puts(input);
 puts("Done.\n");

 return 0;
}
#include <ctype.h>
C	Primer	Plus	Sixth	Edition	Programming	Exercise	Selected	Answers
25
char * getword(char * str)
{
 int ch;
 char * orig = str;
// skip over initial whitespace
 while ((ch = getchar()) != EOF && isspace(ch))
 continue;
 if (ch == EOF)
 return NULL;
 else
 *str++ = ch; // first character in word
// get rest of word
 while ((ch = getchar()) != EOF && !isspace(ch))
 *str++ = ch;
 *str = '\0';
 if (ch == EOF)
 return NULL;
 else
 {
 while (ch != '\n')
 ch = getchar();
 return orig;
 }
}

为什么输入空格和结束符时没有结束程序