The mobile phone is recharged through the postal savings bank card, and the transaction code is required after entering the SMS verification code. What is the transaction code?

The transaction code is generally a bank card password.

Password is a confusing technology, hoping to turn normal (identifiable) information into unrecognizable information. Of course, for a small number of people, these unrecognizable information can be reprocessed and recovered. Password is a general term for "password" in Chinese. In fact, the "password" entered when logging in to websites, e-mails and withdrawing money from banks should be strictly called "password" because it is not the original "encryption code", but it can also be called a secret number. A symbolic system (such as a message) that is mainly limited to personal understanding. Such as cipher telegrams and cipher typewriters.