Allocate an ODBC environment.

For example:

SQLRETURN rc;
SQLHENV   env;
rc = 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:

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

Allocate an ODBC connection item.

For example:

rc = 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:

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

By default, ODBC operates in autocommit mode. This mode is turned off by setting SQL_AUTOCOMMIT to false.

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 (rc == SQL_SUCCESS || rc == SQL_SUCCESS_WITH_INFO) 
{
   printf( "dbc allocated\n" );
   rc = SQLConnect( dbc,
      (SQLCHAR *) "SQL Anywhere 16 Demo", SQL_NTS,
      (SQLCHAR *) "DBA", SQL_NTS,
      (SQLCHAR *) "sql", SQL_NTS );
   if (rc == SQL_SUCCESS || rc == SQL_SUCCESS_WITH_INFO)
   {
       // Successfully connected.

Every string passed to ODBC has a corresponding length. If the length is unknown, you can pass SQL_NTS indicating that it is a Null Terminated String whose end is marked by the null character (\0).