FORTRAN 90: Functions, Modules, and Subroutines (pdf format)

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Rule #1 • An item declared within a subprogram is not accessible outside that subprogram. • Item is ‘local’ to that subprogram. • Item is ‘global’ if declared in the main program.
Rule #2 • A global entity is accessible throughout the main program <strong>and</strong> in any internal subprograms in which no local entity has the same name as the global item. • Factorial example • Warning: Although global variables can be used to share data between the main program <strong>and</strong> internal subprograms, it is usually unwise to do so. – Reduces the independence of the various subprograms making modular programming more difficult. – Changing a global variable in one part of a program changes it throughout the program, including all internal subprograms. • Statement labels are not governed by scope rule #2. – FORMAT statements in the main program cannot be used within subprograms. • IMPLICIT is global. – Not necessary to include it in these subprograms.
Page 1 and 2: FORTRAN 90: Functions, Modules, and
Page 3 and 4: Functions • Intrinsic, or library
Page 5 and 6: Specification/Execution Sections
Page 7 and 8: Main program syntax • This subpro
Page 9 and 10: Method of Execution • Main progra
Page 11: Scope • May be several points whe
Page 15 and 16: Modules • Often similar calculati
Page 17 and 18: Translation to source program • T
Page 19 and 20: What are all these file types? •
Page 21 and 22: External Subprograms • Attached a
Page 23 and 24: • subroutine heading specificatio
Page 25 and 26: yet different • Functions are des
Page 27 and 28: Subroutine syntax • Subroutine he
Page 29: Argument association • Coordinate

FORTRAN 90: Functions, Modules, and Subroutines (pdf format)

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