
Excess-3 - weinzierl
https://en.wikipedia.org/wiki/Excess-3
======
timsneath
I've read this three times, and I confess I still don't understand what
Excess-3 is or how it's encoded. While this isn't my area of expertise, I have
a degree in computer science so one might reasonably assume this should be
trivial to comprehend.

This seems to be a challenge for Wikipedia: certain types of technical and
mathematical material are explained in terms that are esoteric enough
("pseudo-tetrade"?) that only the people who already understand them can
follow the explanation.

Even something simple enough to be taught at middle-school level (e.g.
Fibonacci sequence) becomes a page of dense mathematics on the Wikipedia page:
[https://en.wikipedia.org/wiki/Fibonacci_number#Matrix_form](https://en.wikipedia.org/wiki/Fibonacci_number#Matrix_form)

I wonder if this can ever be addressed with some form of adaptive content?

~~~
jws
A decimal digit is encoded in 4 bits as its usual encoding plus 3. Thus 0 is
0011 and 5 is 1000.

Some nice things which happen are…

\- the carry bit out of your 4 bit adder is the carry bit from the decimal
add. (Your two digits plus their two threes makes sixteen)

\- you never have more than three identical bits in a row (5 if you
concatenate digits). This can be important for any kind of self clocked data
stream. Too long without transitions and you aren’t really sure how many bits
the sender meant because your clocks are a little off.

\- it has a reasonable way to represent negative numbers.

One significant downside was that on each add you had to take a 3 back out.

