getting the correct column size....

Hi all!

I am developing an application (on Mac OS X, using ObjC and Cocoa)  
the uses
the libpq client library. Now I have difficulties to get the correct  
size of several sql types.

for example:
A table as a char(10) column.
When I get the size via PQfmod() I get 14 as size value.

2. example:
My table has a decimal(19,4) field (19=precision, 4=scale).
How can I get the 19,4 value via the client lib?

I did not find any other way to get column sizes.

How can I get the values?

Thanks for any help!

Regards,
Ralf