Re: what is the meaning of Datum?

Tom Lane wrote:
> Luca Ferrari <fluca1978@infinito.it> writes:
>
>> ok this is a silly question, but I've got a doubt: what is the exact meaning
>> of Datum?
>>
>
> It's the backend-internal representation of a single value of any SQL
> data type.  The code using the Datum has to know which type it is,
> since the Datum itself doesn't contain that information.  Usually,
> C code will work with a value in a "native" representation, and then
> convert to or from Datum in order to pass the value through
> data-type-independent interfaces.
>
>             regards, tom lane
>
>
And how this convertions will be made ?
Are there internal functions to do this ?

Thanks.
-Tedy