The letter-number pairs are the slots, and the arrows are the phase (reader ↥, compute ▸, call ↱, pick ?, writer ↧, conform =, transfer ↦). The symbol choice is from http://millcomputing.com/instructions.html, with the phase column collapsed.
Though if I had my say it’d be reader ⤒, compute ⏩, call ↺, writer ↧, conform ♺, transfer ⤷.
