convert between characters and values
// character to ASCII value: use ?
// string to integer: use []
// integer / number to character: use .chr
//more info: "Ruby Cookbook", O'Reilly
1 2 ?a # => 97 3 ?\n # => 10
// string to integer: use []
1 2 'a'[0] # => 97 3 'hallo'[1] # => 97
// integer / number to character: use .chr
1 2 97.chr # => "a" 3 10.chr # => "\n"
//more info: "Ruby Cookbook", O'Reilly
