The first versions of ASCII used 7-bit codes, which meant they could attach a character to every binary number between 0000000 and 1111111, which is 0 to 128 in decimal.

Python makes a pretty nice interactive calculator. You can do the other way around, too, with the builtin function bin(x). (And there are also hex() and oct() builtins, if you also need to go back ...

It's not rocket science, but it requires adjusting how one thinks about numbers and numerals. The following binary and hexadecimal examples explain how these alternatives to the decimal-based number ...