I'm developing a scientific calculator for the 2600, in the style of a Casio FX-82, or a TI-35.
For now, it can manage numbers up to 11 digits (2 decimal), both positive and negative, and can perform the four basic operations and square roots. Also, will manage overflow (for now, only for multiplication).
At least I think I'm going to also add some memories, basic trigonometric calculations, logarithm operations and maybe extend it to manage any arbitrary number of decimal digits.
Its use is intuitive, use the left joystick to move the cursor over a number or operation, and fire to select it, something like a real calculator.
This is the first thing I develop for the Atari 2600, so I'm using Batari Basic, but I have experience with assembly programming, so I'm coding some of the math routines in 6202 assembly, so they can run fast enough.
Additions, subtraction and some parts of multiplication are already coded in assembly. Meanwhile, an hourglass can appear if an operation can take some time to perform.
If the right difficulty switch is set to A, the display is not updated while performing calculations, and they run many times faster. I'd like to know what appears if it's used on a CRT screen, as don’t have any available.
I have attached the first prototype (PAL60 / NTSC).