Some feedback. First, let me tell you I love this nifty little app. Very useful indeed. All my comments are just minor things:

• By default it is installed in the Science category. I think it should go to Development, although others might of course think otherwise.
• There is no need for the "Exit" menu entry. In fact people won't expect it and may confuse it for "Edit" as I did - and get a surprise
• Some help would be nice. It did not take me long to work out what the A, B, C registers are for but still.
• Switching to fewer bits and back clears the top bits. This should not happen. At least not in the signed mode: it should sign-extend when switching from e.g. 8 to 16 bits.
• The ASCII fields are not necessarily ASCII. By that I mean non-ASCII values are not suppressed. This can be considered a feature of course.
• It would be nice to have an option to save the current state on exit. I would even welcome that as the default.
• It would be nice to have a "Clear" button, although not really necessary as one could just type 0 in the "dec" or "hex" edit box.
• It would be nice to have a switch between little and big endian. Probably only useful for the ASCII representation and that can be easily reversed so perhaps not that important.
• I am probably too young for that and have never seen the point but some people might like the conversion to/from octal base (did you realize that there is no way to type a decimal integer zero in C? ).

As mentioned, these are all minor things and most of them are just ideas thrown in for a consideration. All in all a very useful thing, thanks for that!