I have a memory from when I was very young of my dad doing the finances. He would sit in his office with a computer on one side and an old-fashioned adding machine on the desk. While he worked on the spreadsheet on the computer, he would use the adding machine for quick calculations.
A year or two ago I had a very similar experience. I walked upstairs to the office and there he was, at the same desk, spreadsheet on one side and calculator on the other. Except it was 2020, and he had long ago replaced the adding machine with an iPad. There was really one noticeable difference between the iPad and the old adding machine: the iPad was awful at the job. My dad was using some random calculator app that was an awkwardly scaled iPhone app with an ugly flashing banner add at the bottom.