# Dev notes — 2023-08-15

## Goals for today

- [x] Review planned changes to simulator
  - [x] 'opcodes' and 'operands'
  - [x] fix $00 contains $20 bug

- [ ] Review planned changes to the system
  - [x] CHP, CFC -> FHP, FTG -- dev note 2023-08-07
  - [ ] ? 5x5 display
  - [ ] bank-switching flag in 0 page

- [ ] Implement any changes necessary for writing a program?
- [ ] Write a program
  - [ ] LOGO turtle on 5x5?

## Overflow flag

Ken Shirriff, [The 6502 overflow flag explained mathematically](https://www.righto.com/2012/12/the-6502-overflow-flag-explained.html):

> A common definition of overflow is `V = C6 xor C7`. That is, overflow happens if the carry into bit 7 is different from the carry out.