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

# Out parameters
**Out parameters** are the parameters that are passed to get the output of a function/procedure. The out parameters are passed by reference. Passing parameters by reference means that the function/procedure gets the memory address of the parameters. The changes made to the parameter passed by reference are not discarded when the function/procedure returns, and are propagated back to the calling block.

# Variable parameters vs. out parameters
**Variable parameters** are also passed to a function/procedure by reference. The difference between *variable parameters* and *out parameters* is as follows:

|Variable parameters|Out parameters|
|---|---|
|The initial value of *variable parameters* before entering the function/procedure is not discarded when entering the function/procedure. This means that the function/procedure can use the current value of its *variable parameters*.|The initial value of *out parameters* before entering the function/procedure is discarded when entering the function/procedure. This means that the function/procedure cannot use the current value of its *out parameters*.
|A *variable parameter* must be initialized before calling the function/procedure.| It is not required to initialize an *out parameter* before calling the function/procedure.



# Syntax

Out parameters are passed to a function using the `out` keyword, as follows:
```pascal
function (out _parameterName_: _parameterType_): _returnType_;
begin
   //function body
end
```

Similarly, out parameters are passed to a procedure using the `out` keyword, as follows:
```pascal
procedure (out _parameterName_: _parameterType_);
begin
   //procedure body
end
```
* `_parameterName_`: The name of the out parameter.
* `_parameterType_`: The data type of the out parameter.
* `_returnType_`: The data type of the return value of the function.

>Note: The `out` keyword is only supported in Delphi and ObjFPC mode.
# Example
Consider the code snippet below, which demonstrates the use of out parameters:

{$mode objfpc}
program function1;
var
   a, b, calSum : integer;
   
procedure sum(out calSum: integer;var a, b: integer);
begin
   
   calSum := a+b;
end;

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

pascal

# Explanation
A function `sum()` is declared in *line 5* and calculates the sum of two numbers passed to it as parameters. The parameters `a` and `b` passed to the `sum()` function are *variable parameters*, and the parameter `calSum` passed to the `sum()` function is an *out parameter*. The return value of the `sum` function is stored in `calSum`.


Variable parameters	Out parameters
The initial value of variable parameters before entering the function/procedure is not discarded when entering the function/procedure. This means that the function/procedure can use the current value of its variable parameters.	The initial value of out parameters before entering the function/procedure is discarded when entering the function/procedure. This means that the function/procedure cannot use the current value of its out parameters.
A variable parameter must be initialized before calling the function/procedure.	It is not required to initialize an out parameter before calling the function/procedure.

What are out parameters in Pascal?

Out parameters

Variable parameters vs. out parameters

Syntax

Example

Explanation