//#define __STDC_WANT_LIB_EXT1__ 1#include <stdio.h>#include <string.h>int main(void){  char *unit_words[] = {"zero", "one","two","three","four","five","six","seven","eight","nine"};  char *teen_words[] = {"ten", "eleven","twelve","thirteen","fourteen","fifteen","sixteen","seventeen","eighteen","nineteen"};  char *ten_words[] = {"error", "error","twenty","thirty","forty","fifty","sixty","seventy","eighty","ninety"};      //上面的是什么意思？    char hundred[] = " hundred";  char and[] = " and ";         //就是这个字符。 and字符串有5+1个字符，其中一个是结束字符。    char value_str[50] = "";  int value = http://www.mamicode.com/0;                     // Integer to be converted  int digits[] = {0,0,0};            // 这是什么意思?digit这个数组里面有三个值？  int i = 0;  printf("Enter a positive integer less than 1000: ");  scanf_s("%d",&value);  if(value >= 1000)    value = 999;  else if(value < 1)    value = 1;//为什么不直接显示错误，而要非执行这个区间的值  while(value > 0)  {    digits[i++] = value % 10;//求得各位数！    value /= 10;//十位以上的数字  }  if(digits[2] > 0)  {    strcat_s(value_str, sizeof(value_str), unit_words[digits[2]]);// unit_WORDS[digits[2]]这是什么意思？圆程序？    strcat_s(value_str, sizeof(value_str), hundred);    if(digits[1] > 0 || digits[0] > 0)      strcat_s(value_str, sizeof(value_str), and);  }  if(digits[1] > 0)  {    if(digits[1] == 1)      strcat_s(value_str, sizeof(value_str), teen_words[digits[0]]);    else    {      strcat_s(value_str,sizeof(value_str), ten_words[digits[1]]);      if(digits[0] > 0)      {        strcat_s(value_str, sizeof(value_str), " ");        strcat_s(value_str, sizeof(value_str), unit_words[digits[0]]);      }    }  }  else    if(digits[0] > 0)      strcat_s(value_str, sizeof(value_str), unit_words[digits[0]]);          //最终一步到位的输出，程序相当简洁，上面的构思巧妙  printf("\n%s\n", value_str);  return 0;}