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SpecialSymhol = "+" I "-" I "*" I "I" I "=" I "<>" I "<" I "<=" I ">" I ">=" I "(" I ")" I "[" I "]" I ":=" I "." I " .. " I " :" I ";" I "i" I WordSymhol. 

WordSymhol = "di v" I "mod" I "nil" I "in" I "or" I "and" I "not"I"if"I"then"I"else"I"case"I"of"l "repeat" I "until" I "while" I "do" I "for" I "to" I "goto" I "downto" I "begin" I "end" I "with" I "const" I "var" I "type" I "array" I "record" I "set" I "file" I "function" I "procedure" I "label" I "packed" I "program" . 

The following alternative representations are standard: 

<img src='content_image/791927.jpg'>

Many ofthe symbols are constructed from letters and digits. Except within a character string, a lower-case letter is equivalent to the corresponding upper-case letter. 

Letter = "a" I "b" I "c" I "d" I "e" I "f" I "g" I "h" I "i" I "j"I"k"I"l"I"m"I"n"I"o"I"p"I"q"I"r"l "s"I"t"I"u"I"v"I"w"I"x"I"y"I"z" . 

Digit = "0" I "1" I "2" I "3" I "4" I "5" I "6" I "7" I "8" I "9" . 

Identifiers serve to denote constants, types, variables, procedures, functions, fields, and bounds. Directives are used in procedure and function declarations. 

Identifier = Letter I Letter I Digit} . 

Directive = Letter I Letter I Digit} . 

The spelling of a word symbol, identifier, or directive is the entire sequence of specific letters and digits that it contains. No identifier or directive may have the same spelling as a word symbol. 

