"A Walk Through 'Visible Storage'", section 2 of 6, by LEN SHUSTEK
From "CORE 2.3", a publication of The Computer History Museum.

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It wasn't until the 1940s that electronic devices we recognize as being similar to modern computers began to appear. Here is a small part of one of the first, the ENIAC,

Photo by Michael Dubinsky
("Electronic Numerical Integrator and Calculator"), designed during WWII at the University of Pennsylvania to compute ballistics tables for the Army.

Unfortunately ENIAC, a room-sized monstrosity with 18,000 vacuum tubes, was finished too late to help with the war effort. And, it wasn't really a computer in the modern sense, because it didn't have a program stored in memory that could be easily changed.

The "stored program" breakthrough occurred June 21, 1948 at the University of Manchester on a test computer called "The Baby" that at the time wasn't considered important enough to preserve so it no longer exists. But starting in 1949 and based on that idea, true computers as we know them today began to appear. The Johnniac,

Photo by Michael Dubinsky
was one of the first generation of computers in that modern design, and the only one ever named for John Von Neumann, the brilliant Hungarianborn mathematician who played an important role in the invention of the modern "stored program" computer. The Johnniac was built by the Rand Corporation of Santa Monica, California, and was an approximate copy of the machine built under Von Neumann's supervision at the Institute for Advanced Studies in Princeton, New Jersey, It wasn't exactly the same, but that was ok because in those days the notion of computers sharing program "software" (a term not yet invented) was not an issue-if you had a computer, you wrote programs specifically for it and no other machine used them.

These new contraptions were clearly going to be useful for many different things. But in the early 1950s if you wanted a computer for, say, calculating some physics equations for your PhD dissertation, you had a problem. Computers had been invented, but you couldn't buy one. If you were determined enough, like Gene Amdahl at the University of Wisconsin, you simply built one for yourself. This is his WISC

Photo by Jessica Huynh
from 1952, the "Wisconsin Integrally Synchronized Computer." In the process Amdahl decided that building the computer was more fun than doing the physics, and he went on to design many important computers that were manufactured first by IBM and later by his own eponymous company. But this early handcrafted WISC, like many of the objects in our collection, is a one-of-a-kind item. If you look closely you can also see that it is the only object in our collection that is perforated with bullet holes, a punishment many of us have wished but not dared to inflict on our own computers. For the real story on the bullet holes, visit the Museum and ask a docent.


The biggest impediment to building computers in the early 1950s was the lack of a good way to store data-which was now both numbers and programs. Early machines experimented with a wide variety of bizarre schemes, from vacuum tubes that conducted a current or not, to CRT screens with spots of light and dark, to this strange-looking delay line from the UNIVAC I,

Photo by Jessica Huynh
that stored information as sound waves traveling through metal tubes filled with liquid mercury.

The biggest impediment to building computers in the early 1950s was the lack of a good way to store data which was now both numbers and programs.

The 1953 breakthrough that caused computers to flourish was the magnetic core:

a small ferrite doughnut that could be magnetized either clockwise ("zero") or counter-clockwise ("one"). An Wang at Harvard pioneered the use of core, and Jay Forrester

at MIT made it practical by inventing a matrix scheme using two wires at right angles to read and write individual cores without having a separate wire for each one.

Magnetic core became the dominant computer memory for 25 years until semiconductor memories were invented. Forrester, who was inducted as a Museum Fellow in 1995, decided shortly after his invention that all the really interesting problems in computer hardware had been solved, and he moved on to other fields where he made equally brilliant and seminal contributions.

One of the first large computers that core memory made possible was a huge system for the military with the combat-speak name of "Semi-Automatic Ground Environment" or SAGE.

Photo by Michael Dubinsky
This photo shows only a few of SAGE's 51,000 vacuum tubes, every one of which had to be working simultaneously in order for the computer to work.

There were 46 SAGE

Photo by Michael Dubinsky

Photo by Michael Dubinsky
computers built. One machine was installed in each of 23 underground bunkers located in the U.S. and Canada, and each location had a hot- standby backup waiting to take over. Their purpose was to process radar data and detect Russian piloted bombers coming over the north pole toward the U.S. Despite all the tubes, these machines were incredibly reliable and were operated until the early 1980s. The fact that by then Russia had long since developed Intercontinental Ballistic Missiles (ICBMs) and SAGE was not fast enough to track them usefully didn't put them out of business. Perhaps the Russians didn't know SAGE's limitations.

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