Table with differerent Data Types

Hi,

I´m trying to do the follow: create a table like:
create table t(
cod serial,
data_type char(10),
value ???
);

I would like to do the follow the table would tell me what data type
its the value. For instance:

insert into t values(1, 'Integer', 12);
insert into t values(2, 'String', 'test');
insert into t values(3, 'Float', 1.23);

How can i do that? Its that possible? How Can i solve this problem?

Thanks a lot