The HP 48 followed a couple of decades of HP calculators using RPN (hardly famous, just an evolution). HP’s first calculator used RPN. I recommend https://www.

The HP 48 followed a couple of decades of HP calculators using RPN (hardly famous, just an evolution). HP’s first calculator used RPN. I recommend https://www.hpmuseum.org/ https://www.hpmuseum.org/ for more details.