Execution of a Fortran program begins with the first executable statement in the main program and ends with a STOP statement anywhere in the program or with the END statement of the main program.
The form of a main program is
program-stmt is a PROGRAM statement.
use-stmts is one or more USE statements.
specification-part is one or more specification statements or interface blocks.
execution-part is one or more executable statements, other than RETURN or ENTRY statements.
internal-subprogram is one or more internal procedures.
end-stmt is an END statement.