I originally posted this to the Apple II forum, but I thought I might get more replies in the Apple I forum.
I recently bought a Brain Board Version 1 on eBay for my Apple II computer. The card works great. The card design provides a nice, efficient way to get an Apple-1 emulator in my Apple II. My problem is that my Apple II keyboard is not perfect. Some keys will produce two characters instead of just one. This was fine with the Apple II as I could just use the left arrow to 'backspace' over the extra character and type over it. But, to my knowledge, the Brain Board Apple I emulator does not have a 'backspace' key. Is there a 'backspace' key for the Apple-1 emulator on the Brain Board?
The "rubout" or RUB key or "Delete" key on the Apple IIe is the underscore key when using the Apple-1 monitor. The Apple II and Apple II plus don't have an underscore key.
The Escape or ESC key in the Apple-1 monitor works like Ctrl+X (Cancel) on the Apple II cancelling the entire line.
I don't have a Brain Board, but I wrote some software that is similar.
https://mastodon.social/@mmphosis/113507116665821296
The original monitor of the Apple-1 takes an underscore (ASCII 0x5F) character. This underscore is added in the terminal to mark the previous character is to be ignored, it does not remove the previous character from the screen. For example, typing 23 + _ + 4 + ENTER should show the memory contents of 0x24 in the zero page. On the display it shows '23_4'.