txt[plen] = (char)c; // append c
txt[plen+xtra] = '\0'; // append '\0' or overwrite c
// If the put area already contained \0, output will be truncated there
txt[plen] = (char)c; // append c
txt[plen+xtra] = '\0'; // append '\0' or overwrite c
// If the put area already contained \0, output will be truncated there