[rct42]

Same for me. My note book is A4 sized (lots of space), has a hard cover (easy to write with while out "in the field") and the pages are not easily removed (so I don't loose notes).

While I do write a lot of notes in it, I also like to draw block diagrams and high level designs of systems.

While some of this could be done on a tablet, I also try to reduce the amount of screen time on my eyes. I started this habit since starting my Masters 10 years ago.

[rodolphoarruda]

Me too. A4 sized grid notebook, and I use it in the landscape position. My notes are a mix of schemas and written text. When I'm happy with my work I take a picture of it using the Evernote app and upload it to its cloud. Curiously enough, the app applies some sort of "filter" to the picture that removes the original grid lines, making the drawings cleaner, which is convenient sometimes.