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What are untyped parameters in Pascal?

Syed Muhammad Ali Mustafa

Parameters in Pascal are the variables passed to a function or procedure. We use parameters to pass data we want to use in a function or procedure. There are four types of parameters in Pascal:

Untyped parameters

Untyped parameters are parameters that have no type. Variable, constant, and out parameters can also be untyped.

Syntax

Untyped parameters are passed to a function, as follows:

function (_parameterType_ _parameterName_): _returnType_;
begin
   //function body
end

Similarly, untyped parameters are passed to a procedure, as follows:

procedure (_parameterType_ _parameterName_);
begin
   //procedure body
end
  • _parameterType_: The type of the parameter. It can be var for variable parameter, const for constant parameter, or out for out parameter.
  • _parameterName_: The name of the untyped parameter.
  • _returnType_: The data type of the return value of the function.

Note:

  • The address of the untyped parameter is passed to the function/procedure.
  • The function/procedure does not know the data type of the untyped parameter.
  • An untyped parameter must be typecasted to use in an assignment or assign a value to it.

Code

Consider the code snippet below, which demonstrates the use of the untyped parameters.

program function1;
var
   a, b, calSum : Integer;
   
function sum(const a, b): Integer;
var
a2, b2 : Integer;
begin
   a2 := Integer(a);
   b2 := Integer(b);
   sum := a2 + b2;;//store return value in variable having same name as the name of function
end;

begin
   a := 5;
   b := 10;
   writeln('');
   calSum := sum(a, b);
   writeln(a, ' + ', b, ' = ', calSum);
end.

Explanation

A function sum() is declared in line 5 that calculates the sum of two numbers passed to it as parameters. The parameters passed to the sum() function are untyped parameters. The untyped parameters a and b are typecasted to integers in line 9 and line 10 respectively. After typecasting, the sum is calculated and returned.

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Syed Muhammad Ali Mustafa
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