The syntactic marks of a representation language, both symbols and typographical display features, are realized as a set of worthy characters and the newline. Effectively, an Algol 68 program is a sequence of worthy characters and newlines. The worthy characters are:
a b c d e f g h i j k l m n o p q r s t u v w x y z
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
0 1 2 3 4 5 6 7 8 9
space tab " # $ % & ' ( ) * + , - . / : ; < = > [ \ ]
^ _ | ! ? ~ { }
Some of the characters above were considered unworthy by the original Standard Hardware Representation:
!It was considered unworthy because many installations didn’t have a
vertical bar base character, and ! was used as a base character
for |. Today every computer system features a vertical bar
character, so ! can qualify as a worthy character.
&The Revised Report specifies that & is a monad, used as a
symbol for the dyadic and operator. The Standard Hardware
representation decided to turn it into an unworthy character,
motivated by the fact that no nomads existed for the other logical
operators not and or, and also with the goal of
maintaining the set of worthy characters as small as possible to
improve portability. Recognizing that the first motivation still
holds, but not the second, this compiler re-instates & as a
monad but doesn’t use it as an alternative representation of the
and operator.
~The Standard Hardware Representation vaguely cites some “severe
difficulties” with the hardware representation of the tilde
character. Whatever these difficulties were at the time, they surely
don’t exist anymore. This compiler therefore recognizes ~ as a
worthy character, and is used as a monad.
?The question mark character was omitted as a worthy character to limit
the size of the worthy set. This compiler recognizes ? as a
worthy character, and is used as a monad.
\Back-slash wasn’t included as a worthy character because back in 1975
it wasn’t supported in EBCDIC (it is now). This compiler recognizes
\ as a worthy character.
tabThis compiler recognizes the tabulator character as a worthy character, and it is used as a typographical display feature.