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Page 24 Computer Languages for Engineering - SS 132.5.5 Declaration of Variables and Constants in FORTRAN 90The declaration of variables in FORTRAN 90 is slightly different from the FORTRAN 77 format and isgiven by the following statement.Data Type :: List of VariablesIn the following example the three integer variables month, day and year are declared. In the secondline the real variable seconds is declared. The character variables which should store some stringsshould be declared with a properly length. The first declaration shows the declaration with an explicitlength parameter, the second declaration uses only the value of the length.Listing 2.8: Declaration in 90++1 INTEGER :: day, month, year2 REAL :: seconds3 CHARACTER(len = 10) :: prename4 CHARACTER(20) :: famnameIn the following example you can see how to initialize the just declared variables. This is like declarationand initialization in the language C simply within one step. So the obsolete statement DATA is no longerneeded and can be canceled from modern FOTRAN 90 sources (see also section 2.5.4).Listing 2.9: Declaration and Initialization in 90++1 INTEGER :: day = 16, month = 10 , year = 20102 REAL :: seconds = 10.53 CHARACTER(len = 10) :: prename = ’Ernst’4 CHARACTER(20) :: famname = ’Baeck’The following example shows, how to declare parameters (constants). You see the code is very simularcompared with the previous code. Only the attribut PARAMETER was added. Within the first code thecontent of the variables can be changed by an assignment. Within the second code, we have declaredparameters and the content of this parameters can not be changed, because a parameter is fixed. So yousee, that the FORTRAN 77 statement PARAMETER, now obsolete, is also no longer necessary and canbe deleted from modern FORTRAN 90 code (see also section 2.5.4).Listing 2.10: Declaration and Parameters in 90++1 INTEGER, PARAMETER :: day = 16, month = 10 , year = 20102 REAL, PARAMETER :: seconds = 10.53 CHARACTER(len = 10), PARAMETER :: prename = ’Ernst’4 CHARACTER(20), PARAMETER :: famname = ’Baeck’2.6 OperatorsFortran offers a set of operators, which are offered from the most computer languages. Fortran usesthe same precedence as we know form the mathematics. The power operation has the strongest bindingfollowed by the point operators (products and divisions) followed by the line operators (plus and minus).Unary operators will always be applied first. To change the standard precedence of the operators we uselike in mathematics parenthesis to dictate the way a formula should be evaluated.E. Baeck