text: //
  // Created by ahogek on 1/10/22.
  //
  
  #include <stdio.h>
  
  /* lower函数：把字符c转换为小写形式;只对ASCII字符集有效 */
  int lower(int c) {
      if (c >= 'A' && c <= 'Z')
          return c + 'a' - 'A';
      else
          return c;
  }
  
  int main() {
      printf("%c", lower('C'));
  }