Stephen Wolfram:

I never liked calculational math, and was never good at it. But starting around the age of 10, I became increasingly interested in physics–and doing physics required doing math.
Electronic calculators arrived on the scene when I was 12–and I immediately became an enthusiast. And around the same time, I started using my first computer–an object the size of a large desk, with 8 kilowords of 18-bit memory, programmed mostly in assembler using paper tape. I tried doing physics with it, to no great success. But by the time I was 16, I had published a few physics papers, left high school, and was working at a British government lab. “Real” theoretical physicists basically didn’t use computers in those days. But I did. Alternating between an HP desk calculator (with a plotter!) and an IBM mainframe programmed in Fortran.
I was basically just doing numerics, though. But in the physics I wanted to do, there were all sorts of algebra. And not just a little algebra. Huge amounts. Expressions from Feynman diagrams with hundreds or thousands of terms, all of which had to be precisely right if one was going to get the right answer.