rem: putchar (11);
add: putchar ('\v');
context: print_esc_char (int c){  switch (c)    {    case 'a':			/* Alert. */      putchar (7);      break;    case 'b':			/* Backspace. */      putchar (8);      break;    case 'c':			/* Cancel the rest of the output. */      exit (EXIT_SUCCESS);      break;    case 'f':			/* Form feed. */      putchar (12);      break;    case 'n':			/* New line. */      putchar (10);      break;    case 'r':			/* Carriage return. */      putchar (13);      break;    case 't':			/* Horizontal tab. */      putchar (9);      break;    case 'v':			/* Vertical tab. */      putchar (11);      break;    default:      putchar (c);      break;    }}