# Dev notes — 2023-09-05

## Re: Blinkenlights

See [2023-08-31](2023-08-31.md#displaying-data-microprocessor-trainer-style)

That earlier note covers hexadecimal.

Here are some new notes on decimal display:

- https://en.wikipedia.org/wiki/Two-out-of-five_code -- used for representing the decimal digits using five bits.

- https://en.wikipedia.org/wiki/Bi-quinary_coded_decimal
  - The Remington Rand 409 and UNIVAC LARC encodings listed on that bi-quinary page are close to what I might want.

**Here's my bi-quinary variation (similar to the IBM 650's):**

    5 q q q q

    ○ ○ ○ ○ ○    = 0
    ○ ○ ○ ○ ●    = 1 
    ○ ○ ○ ● ○    = 2
    ○ ○ ● ○ ○    = 3
    ○ ● ○ ○ ○    = 4
    ● ○ ○ ○ ○    = 5
    ● ○ ○ ○ ●    = 6
    ● ○ ○ ● ○    = 7
    ● ○ ● ○ ○    = 8
    ● ● ○ ○ ○    = 9

## ISA

I think the group and addressing-mode sections need to be smaller, so that you can have more than 16 distinct operations?

## Naming/design variations

- hex keypad version: “microcardiograph”
- toggle switches “minicardiograph”
- etc. 

(allowing diff design for larger punch-card mainframe...)