How to save data even after rebooting

i am working on toradex colibri evaluation board. the data in it gets erased once its rebooted. i want the data to be saved even after rebooting.

Which Toradex module you are using, which OS (WinCE or Linux)?

Can you please provide more information about your environment?
What module and OS are you using?
Please put them as tags to your message, in this way your question will be directed to the people who know how to handle it.

The problem could be, that you saved data to the RAM file system and not to the Flash file system. The RAM file system is lost after every reboot or reset.
If you tell us which module and operating system you are using, we can give you more details on this.
e.g. under Windows CE, you should save your data to \FlashDisk to have it saved persistently.