What a common abbreviation for two's complement code? I've searched on Google, and find "TCC" as a required abbreviation on thefreedictionary. Is it commonly recognized? Or may be there are some other suggestions?
There doesn't appear to be one.
I have a Master's degree in CS and about 25 years in the industry under my belt, and have never heard of one. Of course that isn't authoritative, so I checked out the Wikipedia pages for Two's complement and for Method of Complements. No abbreviation was found in there. There's a fair bit of math going on in those pages to explain the concept. IMHO, if the mathematicians didn't bother with a notation for it, then there probably isn't much of one.
In fact, it looks like "Two's Complement" itself is a bit of an abbreviation. For completeness sake you really have to specify how many bits you are working with, as well as whether you are talking about the number format, or the operation itself.
We used to the term a lot when talking about computer samples (this was 20 years ago), in casual speech we would say "two's comp".
We also had a short hand (we would need a button and "two's comp" is a bit long) but I can not remember right now. Something like 2n-1 but I am really not sure now but it was represented in other software like this too...