CHAR

Characters.

CHAR : 'CHARACTER'

where

CHARACTER : ASCII | \xDIGIT16 DIGIT16

where

ASCII: ALPHANUMERIC | SPACE | [!"$#%&’()*+,-./:; <=> ?@[] \ ˆ`|{}˜]

and

DIGIT16: [a-f] | [A-F] | [0-9]

and

LETTER       = [a-z] or [A-Z] 
ALPHANUMERIC = [0-9] or LETTER or _