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Element 87

87●›
I
Interrupt

Stop it, keep what's done, and wait for me.

Esc · stop button · talk over it

First known

Opened

1963CTSS: press the break key and your program stops, is kept just as it was, and waits for you to start it again. MIT Computation Center.

See also: GPT-4o barge-in: talk over the model and it stops, 13 May 2024.

“the quit signal is generated by depressing and relasing the break key ... machine conditions and the status of memory are preserved for inspection, modification, or re-entry.”

The guide calls the stopped program 'dormant', not dead, because 'the user may still restart or examine his program'.

Someone opened the dated document itself. The source.

  • ReadingValue

Specimen № 87 — operate freely

Stop it mid-photo (Esc works too). Then try pulling the plug.

Fig. 87 — Interrupt

000 readings · idle

Anatomy of Interrupt

  1. 01Stop
    You
    Presses stop, or Esc.
    It
    Takes no new step from that moment.
  2. 02Keep
    You
    Sees what was finished.
    It
    Leaves every completed step exactly as it is.
  3. 03Put back
    You
    Finds nothing half-done.
    It
    Returns the step in flight to how it was before.
  4. 04Wait
    You
    Decides what's next.
    It
    Waits to be told: resume, redirect, or start again.

Phases light as the specimen above registers them. The dark ones are the ones it can't sense.

Lineage

Time-sharing gave every terminal a key that interrupts the running program, which is why Ctrl-C still stops one. Database transactions supplied the other half of the promise in the 1970s: a step either completes or is rolled back, never left half-done.

Descends from
Interrupt
Gave rise to

Under delegation

Mutates

  1. Survives
  2. Mutates
  3. Dissolves

Stopping a program used to mean killing it. Stopping an agent has to mean something gentler: keep what it finished, undo what it was halfway through, and wait to be told. Without that middle promise, every stop leaves a mess for someone to find later.

Becomes

Down the Signal column

  1. it reactsPPress
  2. it followsHHold
  3. it targetsOOpen
  4. it remembersScSchedule
  5. it connectsNNotify
  6. it guessesWWake
  7. it actsIInterrupt

Read down and Press gets heavier: each step is the same act, on a machine that keeps track of more.

Bodies

The act stays put while the hardware changes. These are some of the forms Interrupt takes.

  • Esc
  • stop button
  • talk over it