Types of parameters

*Value type - Using these parameters we can send actual parameter value to the formal parameters.
! The formal parameters modifications doesn't affect in the actual parameters.

*Reference type - Using these parameters we can send actual parameter address into the formal parameters.
! The formal parameters modifications affect in the actual parameter.

*Out Type - Using Out parameter we can send formal parameter value into the actual parameter, while working with these parameters we have to initialise values to the formal parameters, out type parameters function can return collection of values.

#'ref' you can read the value of the variable as well as write to it.
#'out' you can only write i.e., you can only change the value of the variable, you cannot read it.