A function normally takes some See "Parameters"(input) and returns a result (output). These are declared with the keyword Function as in the following

Function IntToStr(Value: Integer): string;

The above declaration can be broken down as

Function keyword indicates it is a function that will return a result

IntToStr is the name of the function. This is what you would type into your code

(Value: Integer) is a list of parameters (input). The part before the colon is the name of the parameter, the second part is the data type. Individual parameters are separated with a semi colon (or if they are of the same type a comma)

: string indicates the data type of the function result

A Procedure is a function that does not return a result. It normally takes some See "Parameters" (input). These are declared with the keyword Procedure as in the following

procedure LogInfo (aMesg : string);

The above declaration can be broken down as

Procedure keyword indicates it is a procedure and will not return a result

LogInfo is the name of the procedure. This is what you would type into your code

(aMesg : string) is a list of parameters (input). The part before the colon is the name of the parameter, the second part is the data type. Individual parameters are separated with a semi colon (or if they are of the same type a comma)

Some procedures will modify the parameters passed in. In this way a procedure can be thought of as returning a result. If this is the case the parameter will be prefixed with the keyword var. An example of this is the Delete procedure declared as

procedure Delete(var S: string; Index, Count:Integer);.

The S parameter is declared with the keyword var therefore whatever variable you pass here as the parameter will be modified (in this case by deleting the given number of characters). Any use of the variable after the procedure call will return the modified value.

Value := IntToStr(MyFloatVariable);

calls the IntToStr function passing in one parameter and assigns the result to the Value variable.

Value := TaxAmount(MyTotalVariable,12.5);

calls the TaxAmount function passing in two parameters separated by a comma.

Normally a function is used on the right hand side of an assignment operator (:=). This assigns the result of the function to the variable on the left of the assignment operator (Refer See "Assignment")

LogInfo('This is the text to log');

calls the LogInfo procedure passing in one parameter.

Delete(MyStringVariable,1,15);

calls the Delete procedure passing in three parameters. This is an example of a procedure that modifies the input parameter. At the end of this procedure call the MyStringVariable will have the first 15 characters deleted. (Refer See "Delete")

Procedures cannot be used on the right hand side of an assignment operator. This is because a procedure does not return a result, therefore it cannot be assigned to a variable (Refer See "Assignment")