763. Writing on Chol HaMoed

104:14 Whatever is necessary as a medical treatment may be done on chol hamoed, both for people and for animals.

104:15 Things like accounts that will be forgotten if they are not written down may be written down on chol hamoed. This is permitted because it's something that would otherwise be lost. Similarly, something that is necessary for the sake of the holiday may be written down but other things may not be written. A personal letter to a friend may be written utilizing some small change, for example by writing the first line on a slant. For everything that's allowed to be written, one may also prepare the pen and ink. (Editor's note: in previous generations, people had to sharpen quills and mix ink. These are obviously no longer concerns.)