WRPN 16c

It uses Reverse Polish Notation (RPN), which uses the ENTER key instead of the "=" (equals) key.

In addition to all the functions you'd expect from an ordinary calculator, WRPN 16c also has many features specifically designed for the computer professional:

• Word sizes from 1-64 bits per word
• Signed math (1's complement, 2's complement, unsigned)
• Logical operators (and, or, xor, not, masks, etc)
• Bit-wise operators (shift, rotate, rotate with carry, etc)
• 32 storage registers
• 4 position stack
• 203 lines of program memory

WRPN 16c is available on other platforms, such as Windows, MacOS, and Linux from the following web site http://www.wrpn.emmet-gray.com

Note: The source code to WRPN 16c is also available!