Problem with data representation.

I have some problem with converting between different data system.
I would like to know how I can convert from signed binary numbers to decimal values, from decimal numbers to signed magnitude, 2's complement, and short floating point format.  Also, it would be better to provide examples with positive and negative values as well as decimal value number (ie. 43.625).

Edit: Just to make clear abit..

I need convertions in the following:

1.) Signed binary numbers <-> decimal values
2.) decimal numbers <-> signed magnitude, short floating point and 2's complement  (Show in 8-bits representation)

I would also like to know does reverse conversion work the same way?....