History of storage: Cuneiform tablets to flash

Computing and human civilisation are useless without data storage. States and cultures have relied on it for more than 5,000 years, but recently we've become rather good at making it fast, capacious and small. Here's a canter through the history of one of our most enduring technologies.

Cuneiform tablet
The first systematic data storage system was the cuneiform writing system, which kicked off in around 3400BCE. Although it evolved into a complete written language, it started off as a way to count and categorise agricultural production and, inevitably, to calculate taxes.

Made by pressing a stylus into a clay tablet, the writing could be rubbed out subsequently — or the tablet could be baked for more permanent storage.

Thousands of legible tablets and other inscriptions survive, an impressive feat that we're unlikely to duplicate with modern technology. However, storage capacity is limited, with a single mobile phone-sized tablet maxing out at around 500 bytes.

Gutenberg printing press
The first data storage system that allowed efficient replication — with all that implies for communication and storage — in the West was Johannes Gutenberg's printing press. Although its output was not much more dense than cuneiform — and the storage medium more fragile — this one invention enabled the Enlightenment and can fairly be said to be the spark that led to all subsequent technology.

Gutenberg invented moveable, mass-producable metal type and oil-based ink, and adapted the agricultural press to the task of producing practically infinite, perfect copies of written work. The printing press was quickly and widely adopted everywhere with the exception of the Arabic speaking world, where it was very slow to be picked up due to a combination of powerful entrenched interests among manuscript makers and technical difficulties in creating acceptable Arabic moveable type.

Mercury delay line
An unusual and marginally practicable data storage system, mercury delay lines were invented for use in second world war radar systems and subsequently saw service in early computers. This one was used in the Lyon's Electronic Office computer, Leo 1, in the early 1950s.

Mercury delay lines store information as a series of ultrasonic pulses sent from one end of a column of mercury to the other. They could store around 500 bits of information, but were difficult to drive and had to be kept in uncomfortably warm surroundings to be efficient.

The same principle, using quartz delay lines, could be found in European colour TV sets until the early 1990s: it's also been proposed that the reflectors left by Apollo astronauts on the Moon could allow the space between it and the Earth to be used as a laser-delay storage system.

Punched card
An icon of early computing, the punched card was very low density but robust — and could be altered and read by unaided, skilled humans at a pinch.

Ultimately deriving from automated weaving machines of the mid-18th century, IBM was the most high profile user of the technology. The form it used was developed by Herman Hollerith — hence the alternate names IBM or Hollerith cards — for the 1890 US Census; his Tabulating Machine Company subsequently became IBM.

The most common size of card could store around 160 characters, although many permutations were used.

Paper tape
Alongside the punched card, paper tape remains fixed in the public mind as symbolic of mid-20th century computing. Developed as storage for teletypes — huge electromechanical devices that were a cross between a typewriter and a telegraph — paper tape came in variable length and could thus store variable amounts of data.

Like punched cards, the holes in the tape triggered optical sensors which turned the patterns in the paper or plastic back into electrical symbols, 5 bits at a time.

One of the most famous uses of paper tape was in Colossus, the reprogrammable electronic computer used by Bletchley Park to crack high-level German codes in the second world war. By replacing the usual mechanical sprocket synchronisation with an optical method, the machine could ingest data from paper tape at a highly respectable 5,000 characters per second. Although the electronics was capable of more, at higher speeds the paper disintegrated.

Paper tape's last hurrah was among radio amateurs, who used it to control radioteletypes until the all-conquering microprocessor saw them off in the mid-1980s.

Magnetic drum
A breakthrough storage invention was the magnetic drum, forerunner of the disk. This example from the mid-'50s IBM 650 had 10,000 characters of storage and acted as the main memory of the computer. The drum was 16 inches long, had 40 tracks and span at 12,500 revolutions per minute.

To ensure uniform, vibration-free rotation, the drums tended to be massive and were driven by powerful motors. An entire tradition of legend and myth has grown up around them, mostly centring on bearing seizures and other catastrophic breakdowns that led to the drums smashing through walls or the complete units walking out of the machine room in clouds of smoke and sparks.

Hard disk
The mainstay of modern computing, the hard disk was invented in 1956 by IBM and hasn't stopped spinning since.

The picture shows six form factors of hard disk, from 8-inch down to 1-inch, and represents the history of the device from the late 1970s through to today. The 8-inch drives had capacities between 5MB and 30MB; the most capacious single 3.5-inch unit today has 3TB.

Although most people know of Moore's Law — the number of devices in an area of silicon will double every two years — the capacity of hard disks has been outpacing that rate of improvement. One of the biggest advances was the discovery of the giant magnetoresistive effect, a piece of quantum physics that went from discovery in 1988 to market in 1998 — and earned its discoverers the Nobel Prize in 2007.

Flash memory
It is the biggest real threat to hard disks — and the fundamental technology that's turned our pockets and handbags into portable datacentres. Flash memory was invented by Toshiba in 1980, and because it is purely semiconductor-based, it has benefited from Moore's Law ever since.

With no moving parts and low power requirements, it has been locked in battle with hard disks for dominance in PCs and larger installations: however, as hard disks' cost and performance continues to improve faster than that of flash, the battle's going to be a long one.

This particular unit, rescued from the ZDNet UK editor's mobile phone, costs around £17 and stores around 16 billion times as much data as the same area of cuneiform.

It is, however, unlikely to survive for more than 5,000 years.

How old is your storage? Let us know in the comments.