Returns the string '00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F 10 11 12 13 14 15 16 17 18 19 1A 1B 1C 1D 1E 1F 7F'x, a character sequence representing the POSIX character class name CNTRL (control characters).

See also class method print (Class Method).