The artefact
Before RAM had a name, it had a glow
In the summer of 1948 the fastest store on Earth was the face of a radar-surplus cathode-ray tube. Freddie Williams and Tom Kilburn had coaxed a standard CRT into holding 1,024 bits — a 32-by-32 raster of charge wells, each well one binary digit, any of them readable in any order at electronic speed. A mercury delay line made a bit wait its turn down a metre of hot metal; the tube simply looked. It was the first random-access memory, and the Manchester Small-Scale Experimental Machine — the Baby — was built around a single tube to prove that a program stored in memory could run at all. On 21 June 1948, it did.
The mechanism
Dot, dash, well
The beam does not paint; it digs. Where it strikes, secondary emission knocks electrons out of the phosphor and leaves a small positive well of charge — a dot for a 0. Stretch the strike into a short dash and the charge settles differently — a 1. That is the dot-dash technique of the Williams patent, and it is why the two marks on the face above have two shapes.
A thin metal pickup plate rests against the outside of the glass. When the beam revisits a spot, the shifting charge underneath induces a pulse in the plate, and the pulse says which mark was there. But the revisit digs a fresh well of its own: every read destroys what it reads, and must be followed at once by a rewrite.
The race
A memory that must keep remembering
The charge in a well leaks away in a fraction of a second. So this memory is not a state — it is an activity: a raster beam sweeping the store, re-reading and re-writing every spot before it fades below readability, forever. The bright line crossing the face above is that sweep; the comet tail behind it is nothing but fresh charge, already leaking.
The simulation runs the artefact’s race slowed for the eye, and it is honest about its own clock: every number below is a constant in the shader, and every number in the HUD is read back from the shader’s framebuffer, not from a scripted mirror.
(sim time — the artefact leaked far faster)
1,024 spots, raster order
below it, a read finds nothing to rewrite
HOLD REFRESH and the race is lost spot by spot — release, and the beam sprints one rescue sweep at scan speed, re-arming every spot still readable. The dead are simply gone.
The store
What the tube is holding
The pattern at rest is not decoration. It is the amended 18 July 1948 listing of the first program ever to run from an electronic memory — Kilburn’s highest-factor routine, as recorded in Geoff Tootill’s notebook. The 21 June original was never written down. Nineteen instructions and eight working values, loaded here with the historic argument: find the highest proper factor of 218.
The real run took about 52 minutes and some 3.5 million operations to answer 131,072 — every one of them fetched from spots of light like these. Words are drawn as the Baby displayed them: least-significant bit leftmost, one 32-bit line per row, function bits at 13–15. Flip a bit above and you are editing the oldest program in the world.