Allocate an ODBC environment.

For example:

SQLHENV   env;
SQLRETURN retcode;
retcode = SQLAllocHandle( SQL_HANDLE_ENV,
  SQL_NULL_HANDLE, &env );

Declare the ODBC version.

By declaring that the application follows ODBC version 3, SQLSTATE values and some other version-dependent features are set to the proper behavior. For example:

retcode = SQLSetEnvAttr( env,
  SQL_ATTR_ODBC_VERSION, (void*)SQL_OV_ODBC3, 0);

Allocate an ODBC connection item.

For example:

retcode = SQLAllocHandle( SQL_HANDLE_DBC, env, &dbc );

Set any connection attributes that must be set before connecting.

Some connection attributes must be set before establishing a connection or after establishing a connection, while others can be set either before or after. The SQL_AUTOCOMMIT attribute is one that can be set before or after:

retcode = SQLSetConnectAttr( dbc,
   SQL_AUTOCOMMIT, 
   (SQLPOINTER)SQL_AUTOCOMMIT_OFF, 0 );

If necessary, assemble the data source or connection string.

Depending on your application, you may have a hard-coded data source or connection string, or you may store it externally for greater flexibility.

Call the ODBC connection function.

For example:

if (retcode == SQL_SUCCESS 
    || retcode == SQL_SUCCESS_WITH_INFO) {
   printf( "dbc allocated\n" );
   retcode = SQLConnect( dbc,
      (SQLCHAR*) "SQL Anywhere 12 Demo", SQL_NTS,
      (SQLCHAR* ) "DBA", SQL_NTS,
      (SQLCHAR*) "sql", SQL_NTS );
   if (retcode == SQL_SUCCESS
         || retcode == SQL_SUCCESS_WITH_INFO){
   // successfully connected.