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Password manager

If you choose a separate, secure password for each service, you have a lot to remember. Password managers assist in remembering and creating secure passwords. They store a virtually unlimited number of passwords in a secure password database. They also provide an easy way to generate strong passwords via built-in password generators. There are some free and good password managers, for example KeePass.

Read why you should use password managers on the page about password manager. There you will also find insctructions on how to install KeePass step by step instruction.

How many different 10-character passwords are there that can contain lowercase letters, uppercase letters, and numbers?

(c) about 839 quadrillion passwords is the correct answer.