Internal Procedures

In F90 program units contain declarations, executable statements, but may also contain internal procedures. A program unit that contains internal procedures is called the host. Internal procedures

• may be called only from within the host;
• have access to all the host declarations;
• can override host declarations;
• may not contain further internal procedures;
• are separated from the host by a CONTAINS statement, for example

PROGRAM

  CALL SUB1()

CONTAINS

  SUBROUTINE ()

  END SUBROUTINE

END PROGRAM