Program statements are grouped into two general classes: executable and nonexecutable. An executable statement specifies an action to be performed. A nonexecutable statement describes program attributes, such as the arrangement and characteristics of data, as well as editing and data-conversion information.
Order of Statements in a Program Unit
The following figure shows the required order of statements in a Fortran program unit. In this figure, vertical lines separate statement types that can be interspersed. For example, you can intersperse DATA statements with executable constructs.
Horizontal lines indicate statement types that cannot be interspersed. For example, you cannot intersperse DATA statements with CONTAINS statements.
Required Order of Statements
PUBLIC and PRIVATE statements are only allowed in the scoping units of modules. In Standard Fortran, NAMELIST statements can appear only among specification statements. However, Intel® Fortran allows them to also appear among executable statements.
The following table shows other statements restricted from different types of scoping units.
Statements Restricted in Scoping Units
Scoping Unit |
Restricted Statements |
|---|---|
Main program |
ENTRY, IMPORT, and RETURN statements |
Module1 |
ENTRY, FORMAT, IMPORT, OPTIONAL, and INTENT statements, statement functions, and executable statements |
Submodule1 |
ENTRY, FORMAT, IMPORT, OPTIONAL, and INTENT statements, statement functions, and executable statements |
Block data program unit |
CONTAINS, ENTRY, IMPORT, and FORMAT statements, interface blocks, statement functions, and executable statements |
Internal subprogram |
CONTAINS, IMPORT, and ENTRY statements |
Interface body |
CONTAINS, DATA, ENTRY, IMPORT2, SAVE, and FORMAT statements, statement functions, and executable statements |
BLOCK construct |
CONTAINS, DATA, ENTRY, and IMPORT statements, statement functions, and these specification statements: COMMON, EQUIVALENCE, IMPLICIT, INTENT (or its equivalent attribute), NAMELIST, OPTIONAL (or its equivalent attribute), and VALUE (or its equivalent attribute) |
1 The scoping unit of a module does not include any module subprograms that the module contains. 2 An IMPORT statement can appear only in an interface body that is not a separate module procedure interface body. |
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