I still have one of those rotary dial desk top phones (but not here at the office).
Technically, my "first" computer was a small kit I made from Radio Shack. It was basically a circuit board on which I attached a few components, and the read-out consisted of some small red LED'S that would light up so I could calculate the number (being displayed) using binary code (a lit LED stood for a 1 while an unlit LED stood for a 0). Instead of using a keyboard to enter numbers, it instead had a photo cell that would move through numbers depending on how many times I would uncover the photo cell to let light hit the photo cell.
I also recall my first real calculator. I won it back when I was a boy with a paper route. I can’t recall how many new subscriptions to the paper I had to sell, but it was quite a few. Back then I thought it was pretty cool (nobody had calculators back then) even though I don’t think it even did square root functions. I also recall the old slide rules we had around the house for homework, and I actually used a slide rule in one class, but then calculators became more mainstream and some really good models for electronic calculations soon came out by Texas Instruments.
Back in the 80’s while attending the University of Utah, I finally had access to a real computer at the University. They were those old Mac’s that had the small black and white screen built right onto the box.
My first "real" computer (bought in 1993) was an IBM with a 25 mega hertz, non-pentium chip. I still have it too, although it sits at home, unused, next to my rotary dial phone.