I want to create some extra fields in catalog->manage product-> general tab section.
give me some suggestion
I think you don't know that Magento uses EAV structure
to store product, customer, customer address, and category data
You can create product attribute from admin panel assign to it general tab from admin
You can follow Magento official doc for it
http://docs.magento.com/m1/ce/user_guide/catalog/attribute-create.html