Subroutines and Functions

• Programmes are often best split into subprogrammes each of which performs a well-defined task --- procedural programming. (Contrast:
  • OO-programming (inheritance, component-driven...);
  • functional programming, e.g., Lisp;
  the former is very trendy, but adds significant run-time overheads.)
  
  
• In Fortran we use SUBROUTINES and FUNCTIONS to construct procedural programmes.

Example

Schematic example:

PROGRAM play_game CALL shuffle_cards CALL deal CALL play CALL display END PROGRAM play_game SUBROUTINE shuffle_cards ... END SUBROUTINE shuffle_cards SUBROUTINE deal_cards ... END SUBROUTINE deal_cards SUBROUTINE play ... END SUBROUTINE play SUBROUTINE display_cards ... END SUBROUTINE display_cards