
Functions in Pascal are declared using the `function` keyword, as shown in the code snippet below:
```C
function _funcName_ (_parameter(s)_: _parameterType_;, _parameter(s)_: _parameterType_;, ...): _returnType_; 
_localDeclarations_
begin
   //function body
end;
```
* **`_functionName_`**: The name of the function.
* **`_argument(s)_`**: The input parameters that are passed to the function.
* **`_parameterType_`**: The data type of the arguments passed.
* **`_returnType_`**: The return data type of the function.
* ﻿﻿**`_localDeclarations_`**: Declarations such as variables, constants, functions﻿, etc.﻿, that are referred ﻿to in the `function body`.


# Examples
## Example 1
Consider a simple example of a function that returns the sum of two numbers:

program function1;
var
   a, b, calSum : integer;
   
function sum(a, b: integer): integer;
var
   tempSum: integer;//local Declaration

begin
   tempSum := a + b;
   sum := tempSum;//store return value in variable having same name as the name of function
end;

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

## Explanation
* *Lines 5-12*: The `sum` function is declared and takes two input parameters, `a` and `b`. The sum function calculates the mathematical sum of `a` and `b` in *line 10* and stores the sum in a local variable, `tempSum`. To return a value from a function, we assign the return value to a variable with the name of the function.
* *Line 17*: The `sum` function is called in line 17 and is passed with `a` and `b` as input parameters. The return value of the `sum` function is then stored in the `calSum` variable.


## Example 2
Another way to return a value from a function is to use the `exit` keyword, as shown below:

program function2;
var
   a, b, calSum : integer;
   
function sum(a, b: integer): integer;
var
   tempSum: integer;//local Declaration

begin
   tempSum := a + b;
   exit(tempSum);
   tempSum := tempSum + 50;
   sum := tempSum
end;

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

## Explanation
* *Lines 5-11*: The `sum` function is declared and takes two input parameters, `a` and `b`. The sum function calculates the mathematical sum of `a` and `b` in *line 10* and stores the sum in a local variable, `tempSum`. To return a value from a function, we use the keyword `exit` that exists from the function and returns its value.
* *Lines 12-13*: Any code in the function body written after `exit` is not executed. This is why *lines 12-13* are not executed. 
* *Line 19*: The `sum` function is called in line 19 and is passed with `a` and `b` as input parameters. The return value of the `sum` function is then stored in the `calSum` variable.


## Example 3
Consider an example of a function with no input parameters:


program function3;
   
function noParam(): integer;
begin
   writeln('This is a function with no parameters');
   noParam := 0;
end;

begin
   noParam();
end.

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How to declare a function in Pascal

Use "function" to declare a function in Pascal, specifying name, parameters, types, and return type.