Wow, just WOW. I have added a serial monitor, and Apple 1 OS

Serial Monitor

Here is the way the monitor work, you load character to $BFE0 like this :

lda #'A'
sta $BFE0

Then you run the program in the emulator like normal, then you open another terminal and you connect to localhost port 8080 using netcat nc like this :

nc 127.0.0.1 8080

And now if you already launch the program, when you connect to localhost (127.0.0.1 is localhost) you will see a A in your terminal !

You can also type in the serial monitor ! Here is a code that show the number of characters typed by using the pixels in the 32x32 screen !

start:
    ldx #$FF
    txs
    ldx #$00

main_loop:
    bit $BFE1
    bpl main_loop


    lda $BFE0

    sta $BFE0

    
    lda #WHITE_COLOR
    sta $0200, x

    inx
    jmp main_loop

Apple 1

This is a very damn big part.

To be short, I have recreated the Apple 1 OS (Wozmon) created by Steve Wozniak. In short I took the code given in the Apple 1 User Manual, modify it to use the Serial Monitor and Keyboard, fix some issue with the prompt. I can even run the classic program from the manual to print all the available characters.

With Wozmon you can also write and read data from the memory so you can show some pixel on the screen !

Here is the program running and the serial monitor.