(char-upcase char)
(char-downcase char)
These convert alphabetic characters to be upper-case and lower-case,
respectively.
> (char-upcase #\a) #\A
(char->integer char)
(integer->char n)
These functions allow conversion between characters and their corresponding
numeric codes so that characters can be manipulated.
> (char->integer #\a) 97> (integer->char (1+ (char->integer #\a))) #\b