--- upcase
--- upcase!

    ASCII ʸϰǥե٥åȤʸˤޤ

    upcase ִʸ֤ޤ
    upcase!  self ѹ֤ޤִ
    ʤä nil ֤ޤ

    $KCODE ŬڤꤵƤʤСɤΰѴ
    Ƥޤޤ(ϡShiftJIS ɤǵޤ)
    դˡ$KCODE ꤷƤޥХʸΥե٥å
    Ͻޤ

        # -*- Coding: shift_jis -*-
        $KCODE ='n'
        puts "".upcase # => 

    downcase, swapcase,
    capitalize ⻲ȤƤ

