Like many engineers, and I suppose accountants, or anyone that works with numbers on a regular basis, I am quite comfortable using a numeric keypad. On the other hand, if you need to use a non-decimal number system, like binary or hexadecimal for retro computing, it’s not nearly as convenient.
There are a few options, however, such as this binary keyboard, that’s designed to input characters only using two keys. Alternatively, on a normal keyboard, 1s and 0s are at least close together on the numpad, or you could simply park a finger over each digit, making binary input relatively easy. On the other hand, inputting hex values is a different story. Not only do you have to input 1 through 10, there’s also the pesky A though F characters, meaning you’ll have to stretch for the numbers on your keyboard or go back and forth between the numeric and “normal” keyboard. Not great.
So why not make something better yourself? If you’d like to create an “extended” numpad, Granz-Tronix has a solution with its Hex Keypad Kit. As shown, digits are arranged in a numeric order from the top down, though you could experiment with different key arrangements depending on how your computer or microcontroller interprets button presses. For that matter, there is no reason why something like this couldn’t be used to control other devices.
As shown in the first image, the current run of these devices has the last row of buttons hanging off of the board. Though fully functional, as of this writing they are available at a discounted price until this batch runs out.