Fortran 90 Handbook

11.8 The Fortran 90 Language Standardenclosed in brackets followed by ellipses (...) may occur any number (includingzero) of times. The ampersand (&) is used to continue a line, just as it is usedto continue a line in a Fortran 90 program. Use of one of the syntactic formsalways produces a syntactically correct part of a Fortran 90 program. Thesesyntactic forms indicate how to construct most of the correct Fortran 90statements, but may not be complete in that they do not describe all of thepossible forms.For example, the following syntax form occurs in Chapter 9. It describes oneform that can be used to construct a direct access formatted WRITE statement.The general syntax for the WRITE statement is quite complex and gives no hintas to which options are allowed for direct access formatting. On the otherhand, this rule is overly restrictive in that it indicates a particular order for theoptions, which is not required by the standard. Nevertheless, using this formalways will produce a correct WRITE statement.WRITE ( [ UNIT = ] unit-number &, FMT = format &, REC = record-number &[ , IOSTAT = scalar-default-integer-variable ] &[ , ERR = label ] &) [ output-item-list ]Another property of the syntactic forms is that the terms used are descriptiveand informal, and they are not necessarily defined precisely anywhere in thebook. If you need to know the precise syntax allowed, refer to Appendix B,which contains all of the syntax rules of the Fortran 90 standard.The Fortran 90 standard (ISO/IEC 1539 : 1991) describes the syntax andsemantics of a programming language. However, the standard addressescertain aspects of the Fortran processing system, but does not address others.When specifications are not covered by the standard, the interpretation isprocessor dependent; that is, the processor defines the interpretation, but theinterpretation for any two processors need not be the same. Programs that relyon processor-dependent interpretations typically are not portable.The specifications that are included in the standard are:1. the syntax of Fortran statements and forms for Fortran programsIntroduction 21Copyright © 1992 J. Adams, W. Brainerd, J. Martin, B. Smith, and J. Wagener