If you have an Android device, the Droid48 app listed there (also at [1]) is worth a plug.  A touch screen on a phone can&#x27;t compete with the awesome tactile keypad those old calculators had, but at least the layout and operation are familiar and I&#x27;ve always got it with me.<p>[1] <a href="https:&#x2F;&#x2F;play.google.com&#x2F;store&#x2F;apps&#x2F;details?id=org.ab.x48" rel="nofollow">https:&#x2F;&#x2F;play.google.com&#x2F;store&#x2F;apps&#x2F;details?id=org.ab.x48</a>