Binary Number help

[Fistandantilis]

I am a bit confused here and need a little push,

1111 = 15
1111 1111 = 255
1111 1111 1111 = 2815? OR 270

the first set of bits goes to a highest value of 15, the first and second set goes to 255. now I am lost at what does the third set make, does the rightmost bit position equat to 1, 0 or does it go to 256
I know this is a bit confusing and I have searched my textbook and the sets of bits they give are all done in sets of 8, I am working with a set of 12, please any help would be greatly appreciated

 

[TheStu]

it isnt 2815.... it is 4095

the form is (2^n)-1 where n is the number of bits involved

 

[walla]

1111 1111 1111 = (2^12)-1 = 4095

 

[Fistandantilis]

I see, Thanks

 

[walla]

Originally posted by: Fistandantilis
I see, Thanks

also, if you need to cheat, you can use the Microsoft calculator in binary mode

 

[Fistandantilis]

Originally posted by: walla

Originally posted by: Fistandantilis
I see, Thanks

also, if you need to cheat, you can use the Microsoft calculator in binary mode

]
No No, cant cheat I need to know this stuff, but just to make sure that I am on the right track, does 617 in octal = 110001111? I think it does and I really hope you all agree, please let me know, I got a test tomorrow and for some reason I cant remember any of this stuff.
**EDIT**
and does 110001111 binary = 18F in hex?