How Windows Password Cracking Programs Work

Please excuse my lack of technical understanding of windows password cracking 
software.

My question is whether windows password cracking programs has to do with how 
these programs work.

Is it correct that they do not crack a password one character at a time?  That 
is, the password cracking programs aren't able to determine that they have 
cracked the first character, or the first two or first three characters?  

Also, is it correct that password cracking programs aren't able to determine - 
ahead of time - how long a windows password is?

Thanks.


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