Nowadays I always see many persons selling bitcoin adder / bitcoin generator or bitcoin hacker software claiming that these are creating 1 bitcoin or more.
I am unable to believe authenticity of their claim.
Can any one make me clear whether these programs work or merely are scams.
AFAIK no such thing is possible. Could you please describe where this balance is supposed to be created?
You could obviously change your local record of the blockchain to reflect added balance, however, no other Bitcoin node would accept payments funded from that balance.
Well it's possible. See https://yourprivatekeys.online . If your went through the entire site, would take hundreds of thousands of years, you would have the private key to every bitcoin wallet that has a balance. The chances are very small that you would find some thing but you could get lucky.