Prior to the ODBC 3.5 standard, all ODBC access to function calls and string data types was through ANSI encoding (either ASCII or DBCS). Applications and drivers were both ANSI-based.
The ODBC 3.5 standard specified that the ODBC Driver Manager (on both Windows and UNIX) be capable of mapping both Unicode function calls and string data types to ANSI encoding as transparently as possible. This meant that ODBC 3.5‑compliant Unicode applications could use Unicode function calls and string data types with ANSI drivers because the Driver Manager could convert them to ANSI. Because of character limitations in ANSI, however, not all conversions are possible.
The ODBC Driver Manager version 3.5 or later, therefore, supports the following configurations:
ANSI application with an ANSI driver
ANSI application with a Unicode driver
Unicode application with a Unicode driver
Unicode application with an ANSI driver
A Unicode application can work with an ANSI driver because the Driver Manager provides limited Unicode-to-ANSI mapping. The Driver Manager makes it possible for a pre-3.5 ANSI driver to work with a Unicode application. What distinguishes a Unicode from a non-Unicode driver is the Unicode driver's capacity to interpret Unicode function calls without the intervention of the Driver Manager, as described in .
ANSI application with an ANSI driver