#include <ctype.h>        /*   * Convert a string to lowercase   */   char *lc(char *str)   {      char *t;           for (t = str; *t; t++)      {         /* Convert to lowercase */         (*t) = tolower(*t);      }           /* Done */      return (str);   }        /*   * Convert a string to uppercase   */   char *uc(char *str)   {      char *t;           for (t = str; *t; t++)      {         /* Convert to uppercase */         (*t) = toupper(*t);      }           /* Done */      return (str);   }