Minsky (7,4) Machine

Marvin Minsky's 7-state, 4-symbol universal Turing machine (1967), halting on a demo input.

Sync Tick Turing

Try it live→ Download Database

Machine replay — the (7,4) head halting after 23 steps FULLSCREEN ⤢

Clock Tick — one step per turn

Update Synchronous

States 7 (t0–t6)

Symbols 4

Halts After 23 steps

OVERVIEW

Minsky's (7,4) universal machine as a true Turing machine. Seven control states t0–t6 over a four-symbol alphabet drive the head along a bidirectional, self-growing tape. Minsky's machine was an early milestone in shrinking the universal Turing machine; this scenario runs its exact transition table on a short demo input that brings the head to its halt state after 23 steps, so the whole run is small enough to watch end to end.

A universal machine that actually halts on its seeded input — the bookend to the non-halting universal machines. It pairs a wide control (seven states) with a finite, fully observable run, making it the clearest of the universal scenarios to step through. The same self-growing tape and single-head pattern carry it with no special-casing.

TRAITS

Sync

Advances on a single global clock

Tick

Discrete fixed-step time

Turing

A head reads & writes an unbounded tape

SCHEMA

Linked tables with guaranteed referential integrity.

TABLECOLUMNSDESCRIPTION

cell ID, symbol, has_left, has_right, left_id, right_id, current_state One row per tape square over four symbols, with self-built left/right neighbour references.

head ID, current_id, nc, current_state The read/write head: the cell beneath it and its t0–t6 control state, including the halt state.

LIVE API

Generated REST endpoints. Also exposed as MCP tools.

POST /scenarios/minsky-74/experiments Seed a fresh tape and head

POST /scenarios/minsky-74/experiments/{eid}/run Run the machine to its halt state

GET /scenarios/minsky-74/experiments/{eid}/entities/cell Read the final tape, one row per square

GET /scenarios/minsky-74/experiments/{eid}/events Append-only step log

GET /scenarios/minsky-74/experiments/{eid}/dataset Download the exported dataset

SEMANTIC LAYER

OSI-compatible definition, emitted with the dataset.

# minsky-74.osi.yaml — emitted automatically
semantic_model:
  name: "minsky-74"
  source: "duckdb://minsky-74.db"
  entities:
    - name: cell
      primary_key: id
  dimensions:
    - name: state
      type: categorical
    - name: t
      type: time
  measures:
    - name: row_count
      agg: count
    - name: active
      agg: sum
      filter: "state = 'ACTIVE'"