Fortran 90 Handbook

Fortran 90 SyntaxBB.1 The Form of the SyntaxThis appendix contains a complete description of the Fortran 90 syntax. SectionB.1 describes the form of the syntax. Section B.2 contains the complete syntaxand constraints as they appear in the standard. Section B.3 is a cross referenceof each syntax term, the rule in which it is defined, and the rules in which it isreferenced. A high-level summary of the syntax appears in Chapter 2.The syntax of Fortran programs is described using a variant of the Backus-Naur Form (BNF).B.1.1 Syntax Rules Expressed in BNFThe BNF syntax rules are expressed as a definition; the metalanguage classbeing defined is first, followed by the symbol is, and finally the syntaxdefinition, as in the following example:goto-stmt is GO TO labelThe term goto-stmt represents the GO TO statement; such terms are callednonterminal symbols or simply nonterminals. The syntax rule defines gotostmtto be GO TO label, which describes the form of the GO TO statement. Thedescription of the GO TO statement is not complete until the definition of labelis given; label is also a nonterminal symbol. A further search for label in theBNF will result in a specification of label and thereby provide the complete727Copyright © 1992 J. Adams, W. Brainerd, J. Martin, B. Smith, and J. Wagener