I was reading a book on digital electronics and the gates with more than two input are drawn differently. I have seen many books that draw schematic in this style. I was wondering what software did they use. I am specifically talking about the way the OR gate is done here.
That doesn't look like any software was used, but a good old-fashioned drawing board, maybe a few symbol templates/stencils/curve templates used by someone who probably is a trained technical draughtman.
Making such drawings is a job where you actually needed quite some expertise, so technischer Zeichner (at least in Germany) is a proper Ausbildungsberuf (a recognised occupation requiring formal training).
Nowadays, you'll find a lot of circuit drawing software, but my guess is that you'd need to extend them quite a bit to make it easy to draw such legacy diagrams.
Other than that, standard vector graphics software can be used to draw anything that primarily consists of geometric elements.
I don't believe this was drawn with any modern software tool. It appears to me to be a reproduction from a late-80s/early-90s era databook from before the days of online/digital datasheets. Go to ti.com and look up some of the CD4000-series logic datasheets that are reminiscent of this period. Dual 2-Input NAND
As to the "wings" on the OR, this is typically done to allow the user to better follow the interconnect of the wires by spacing them out.