Is it permissible to write computer software code on Chol Hamoed?
Rav Stern (page 195-196, teshuvah #56) is quoted as saying:
Question: Is it allowed to write something that's not necessary for Yom Tov via a number machine (ie "a calculator" ), and this is a situation where the letters are not written on paper, but rather are illuminated by electricity on a screen and there is no writing in ink.
Answer: According to Torah law this is not considered writing and there is no exertion at all, and it should not be forbidden. In regard to the prohibition of kindling a fire this is not kindling a fire at all and anyways we do not find kindling a fire unnecessarily forbidden on Chol Hamoed.
If Rav Stern is of the opinion that writing on a calculator is ok, then it's not so farfetched to suggest this could be extended to coding on a computer as well-- but should probably still CYLOR just to be safe.