Busicom 141-PF Emulator - First calculator with a CPU from 1971

RAM 0	Characters																Status
	F	E	D	C	B	A	9	8	7	6	5	4	3	2	1	0	3	2	1	0
Register 0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
Register 1	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
Register 2	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
Register 3	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0

RAM 1	Characters																Status
	F	E	D	C	B	A	9	8	7	6	5	4	3	2	1	0	3	2	1	0
Register 0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
Register 1	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
Register 2	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
Register 3	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0

IO	0	1	2	3
ROM 0	○	○	○	○
ROM 1	○	○	○	○
ROM 2	○	○	○	○
ROM 3	○	○	○	○
ROM 4	○	○	○	○
RAM 0	○	○	○	○
RAM 1	○	○	○	○

Shifters	0	1	2	3	4	5	6	7	8	9
Shift 0	○	○	○	○	○	○	○	○	○	○
Shift 1	○	○	○	○	○	○	○	○	○	○
Shift 2	○	○	○	○	○	○	○	○	○	○

BUSICOM 141-PF

0 decimal points	Truncate Float Round	Overflow Negative Memory

How to use

Start out by typing a few numbers. They won't appear right away. Instead they will only appear after you type in a math operation. Example: 1 2 3 +
Type in a few more numbers, and remember to type the + afterward: 4 5 6 +
Press =

Experiment with different buttons and see what they do.

What is this?

This is an emulation of the Busicom 141-PF, the world's first calculator to run on a CPU, with the world's first single chip CPU, the Intel 4004. Alongside the CPU there are 2 RAM chips, 5 ROM chips, 3 shift register chips, a keyboard and a printer being emulated with perfect synchronization.

Why are there numbers rapidly switching?

The calculator didn't have a display. Instead it had the Shinshu Seiki 102 line printer. The way the printer worked is by rapidly rotating all possible printable characters nonstop. When it was time to print, the calculator would hammer to hit exactly when the right characters came up. View Diagram

Source code

It is my dream to build a chip library for anyone to be able to emulate any chip or board. Therefore, the code is subdivided into several layers of emulation:

Want me to emulate something else? I will be happy to consider it if you could provide me with ROM data. I am interested in most chips built before 1980. It doesn't have to be a CPU either. Shift registers and multiplexers are welcome. Start a discussion in the Chips github repository.

Acknowledgments / Resources

This emulation would be lacking without the resources below:

Unicom 141 User Manual