Modify a field & values all dtabase tables

Hello,

I have problem with BIT fields & NULL values.

I wish to go over all DB tables and perform the following actions:

1. For every table go over its fields.

2. Modify BIT field default value to 0 (false).

3. Modify BIT field's values: NULL to 0 (false).

Can this be implemented in one script ?

Thank you for your help