Cross platform app

Hi all. Newbee here.

I have an existing app created in VisualBasic 5 for Windows OS. The app contains a lot of data ( txt files - about 100Mb total ) and the GUI displays the data in charts / graphs, with many buttons, tick boxes, options etc on the screen.

I am wanting to change the app to work on multiple OS's. I would like something that would be common and operate on iPad, Mac, Win, Linux.

Is there such a platform available, without having to re-code the app for each different OS.

I originally thought Java would be the route to take, but it appears it does not run on the iPad.

What about using the OS's web browsers to display graphs from the local drive ?

All ideas appreciated.

An HTML 5 compliant web app would be your best bet for near universal compatibility. However you'd probably have to host the files on a server. No modern web browser is going to give you access to the local file system. At least no mobile one that I know of. That goes double for iOS. Talk about a security nightmare.

If you are in it for the money, web apps rarely do well. You are reduced to the lowest common UI elements and display. It's a decent solution for businesses looking for a good-enough internal solution, but computer and mobile uses expect polished apps that are consistent with their platform's UI. That's hard to do with a web app, where the browser can do what it wants with your code/site.

But there is a halfbreed sort of app; where a website/app is wrapped in a device specific app. That give you the best of two worlds, where mot of your development is on the web side. On the device you can tweak the UI to look it's best, and you are able to use local storage on the device for files.

You might look at the Adobe Air platform. A few iOS apps created on that platform have done well. I don't know if you can make desktop apps with it, but I believe it supports both Android and iOS.

All this is just babbling on my part, mostly. Everything I've read (all my info on this subject is second hand) says that if you want a top notch app, you write it using that platforms official developer tools and guidelines. Short cuts don't' cut it in the currently very competitive mobile app market.

Good luck.