When Linux ask for my password in command line,my keyboard becomes unresponsive just for that moment or let me put it this way,until i need to write my password my keyboard is unresponsive,but for all other things is fine.or for example,i can input my password when i have a graphic interface but i can't with command line or i can't login to my computer from command line,any idea or suggestion please??
excuse me if my question is doll,i moved from windows to ubuntu just last week,( & i am flying high in sky with ubuntu & digging a very deep hole for windows too!!.)

Just enter your password and hit enter. Nothing is displayed onscreen when you do.

There are two points in not displaying asterisks or other characters while you type the password: first, there's usually no need becuase you'll know yourself how many keys you've pressed (with touch screen virtual keyboards this may be a problem if there's no feedback like vibration), and second, that way nobody can read how many characters your password contains by observing the screen, which means harder brute-force guessing. I've seen some apps (on Windows) that used to print dots or asterisks to the password field, but so that the length of them was different from the actual password length. This supposedly had the idea of hiding the true length of the password from anybody viewing the screen, but could also confuse the writer. I consider it better not to display anything. Passwords are typically less than a couple dozen letters long, and login programs usually allow something like three login attempts before locking the user out, so there's hardly a chance for somebody failing a login because s/he can't see the asterisks or dots on the screen while typing.