Varchar parameter conversion

Hello,

My client program is developed on C++ & ODBC.

It's a Windows Unicode application.

I'm trying to pass a "varchar" parameter value to a user-defined stored
procedure.

Each character of this actual parameter value (which ASC code is greater
than 127) is transformed into some two chars.

This value is stored and bound as a non-Unicode string (traditional
C-string) in the program.

So, some conversion happens for these characters.

It seems to me that it's the ODBC driver's intervention.

Is that right?

And how can I avoid this unwanted conversion?

Additional environment info:

OS: Windows XP SP2

PostgreSQL version: "PostgreSQL 8.2.4 on i686-pc-mingw32, compiled by
GCC gcc.exe (GCC) 3.4.2 (mingw-special)"

ODBC driver version: PostgreSQL Unicode 8.02.04.00

SHOW server_encoding;

"SQL_ASCII"

SHOW client_encoding;

"SQL_ASCII"

Thank you.