Version Compatibility - ESQL/C, Online, SE

I'm building a program that I'd like people to be able to use with Informix SE 5.0 thru 7.10 and Online 5.0 thru 7.10. I assumed I could build the app with ESQL/C 7.10. I'm told now that the program built with ESQL/C 7.10 will not connect to a pre-7.10 SE or Online! Can this really be true? Then I started to think through the options. If I want to use the least common denominator, I'd use ESQL/C 5.0 to build that app, which, I'm told, would then connect to 5.0 and 7.10 of SE and ONLINE. But, how am I going to allow a user to submit a CONNECT TO statement - when the 5.0 compiler does not recognize that syntax - but Online 7.10 requires a CONNECT TO - so the username and password can be supplied. Thanks to anyone who's had experience with this and is willing to share it! BTW - I know for a fact that Oracle DOES provide this kind of backward compatilbility. -- Tom Best, Software Developer | Database Development Group Bentley Systems, Inc | Email: Tom.Best@bentley.com We're on the WEB - http://www.bentley.com