Many calculators will do some conversions for you. In particular, the
standard calculator application that comes as part of Windows will
convert numbers between decimal, binary, octal or hexadecimal. This
calculator can usually be started by looking in the Start ->
Programs -> Accessories menu. When it begins, it generally looks
like a very simple calculator. However, there is a menu title "View"
at the top of the calculator that lets you select between "Standard"
and "Scientific" views. Select the Scientific view.
In scientific mode, you will see a box that allows you to pick between
one of four number systems: Hex(adecimal), Dec(imal), Oct(al), or
Bin(ary). If you want it to convert from decimal to binary, select
decimal mode, then type in a decimal number, then click on binary
mode. In the same way you can convert from binary to octal, and so
on. You can also perform all of the arithmetic operations while
working in any of the number systems. Please note, however, that this
calculator does not handle fractional values in any base other than decimal.
One warning: When working outside of decimal notation, the calculator
can only handle values which fit in 32 bits or less (limit is
slightly less than 4.3 billion). Also, I strongly recommend that you
keep the selection on the right as "Dword" when working in one of the
other bases.