Parameters:

• In the call --- Actual Parameters                                 (In parent's program)
• In the header of definition ---- Formal Parameters        (In child's program)
• The correspondence between actual and formal parameters:
• Positional Parameters:  keep the order.  The 1st actual parameter is bound to the 1st formal parameter and so forth.
• Keyword Parameters: They can appear in any order in the actual parameter list.

e.g. In Ada:
       In the call:     SUMER(MY_LENGTH, SUM => MY_SUM, LIST => MY_ARRAY)
       In the definition:  SUMER(LENGTH, LIST, SUM)
       The 1st parameter is a positional parameter and rest of them are keyword parameters.
       Once keyword parameters used, no more positional parameter after them.
• Default Parameter: when subprogram begins, it assume to pass.

e.g. In Ada:
      In the definition:   function COMPUTE_PAY(INCOME:FLOAT;
                               EXEMPTIONS:INTEGER := 1;
                               TAX_RATE:FLOAT) return FLOAT;
     In the call:   COMPUTE_PAY(INCOME => MY_INCOME, TAX_RATE => MY_RATE)