Fortran is designed for formula translation. Many elementary
Fortran programs will include three components:
The input of data which is stored as variables
The evaluation of formulae using the input data
The output of the results
Here is a simple example:
END PROGRAM Prog2
The next example is similar but uses REAL numbers:
"Enter a real number:"
PRINT *, "The
result is:", x/3.0-0.9E6
END PROGRAM Prog3
In Fortran it is possible to use a variable without explicitly declaring its
type. Variables that are not declared are assumed to be either INTEGER or REAL
depending on the first letter in the name. However, the use of this implicit
typing is not recommended. Moreover, if a variable name is spelled
incorrectly, the implicit typing rule will cause the rogue variable to be
declared leading to erroneous results. In order to avoid this happening, it is
recommended that the implicit typing facility be switched off. To do this,
include the statement IMPLICIT NONE before any type declarations.
Note: FTN95 can be configured so that IMPLICIT NONE is the default for all
program units (see the compiler options /CONFIG and /IMPLICIT_NONE).