programming-for-dummies

584
Creating Subprograms and Functions
This loop runs at least once before checking a condition. If the condition is
True, the loop stops.
The REPEAT-UNTIL loop doesn’t need enclosing BEGIN-END keywords
because the REPEAT and UNTIL keywords serve that function.
Creating Subprograms and Functions
You can create a subprogram (or a procedure) by using the PROCEDURE keyword
as follows:
PROCEDURE Name (Parameter list)
Const
(* Constants here *)
Type
(* Type definitions here *)
Var
(* Variable declarations here *)
Begin
(* Commands here *);
End;
Every subprogram must have a unique name, which usually describes the
purpose of that subprogram (such as Calculate_Credit_Rating or
DenyHealthBenefits). The parameter list declares variables to hold any
data the procedure may need from another part of the program. For example,
a simple parameter list might look like this:
PROCEDURE Name (FirstName : string, Age : integer)
Begin
(* Commands here *);
End;
In the preceding example, a copy of the parameter is passed to the procedure.
If the procedure changes the value of that data, the new value of that
data appears only in the procedure and not in any other part of the program.
If you want a procedure to change the value of a parameter, declare that variable
in the parameter list with the Var keyword, such as
PROCEDURE Name (FirstName : string, Var Age : integer);
Begin
(* Commands here *);
End;
A function is a special version of a subprogram that always returns a single
value. To create a function, use the FUNCTION keyword, such as