Archive: Computer Collector Newsletter / Technology Rewind, Jan. 2004 - March 2006

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A brief history of computer data storage media

by Sellam Ismail

Over the years, computer data storage has evolved from technologies that had applications completely unrelated to computing. New storage technologies were adopted from new inventions as their applicability to data storage became apparent. From punch card technology to magnetic media and finally to optical storage, each new media revolutionized computing by allowing more data to be stored in a smaller space, which naturally allowed an increase in data access speed.

The Punch Card

Punch cards were used for decades in computing applications, but they were actually invented for use in the textiles industry of the 18th and 19th centuries.

Jacques de Vaucanson invented punch cards ( in 1745. They were used to control an automated loom that Vaucanson designed to revitalize the French silk industry. The cards, punched with holes that encoded weaving patterns, were fed into the loom to automatically create complex patterns. This technology was improved upon by Joseph-Marie Jacquard ( in 1804, who improved Vaucanson's system (Jacquard mistakenly gets credit for having invented the concept of the punch card.)

Charles Babbage later adopted the punch card in the 1830s to be used to control loops in his Analytical Engine ( The cards were to be punched with instructions that would be fed into the Analytical Engine for computing formulas (it should be noted that the Analytical Engine was never completed, although functioning replicas were built in the 1990s.)

In the latter part of the 19th century, Herman Hollerith ( adopted the use of punch cards for storing data that would be fed into tabulators he invented for the United States Census of 1890. Each hole punched into a card represented some bit of data, such as age, sex, race, etc. Electric contacts on the tabulating machine would sense the holes in the cards as they were manually fed into the tabulator, resulting in an individual counter for each hole being incremented. Batches of cards (for instance, from an entire town) would then be summed. A new card with that summary data was punched and fed back through to be summed further with other summary cards, ad nauseum, until the population of the United States was computed.

Hollerith formed the Tabulating Machine Company in 1896, which through various mergers and consolidations became the Computer-Tabulating-Recording Company in 1911 - the predecessor of IBM.

In 1914, Thomas Watson, Sr., second in charge at National Cash Register (NCR) joined CTR as the general manager. Watson became instrumental in CTR's growth and in 1924 the company changed its name to International Business Machines (IBM) with Watson heading up the new multinational conglomerate.

Punch cards were a basic staple for IBM data processing machines. Data was entered into the machines by way of punch cards, and results were spit out on punch cards. Special machines called interpreters would translate the raw data on the cards into printed characters. Punch cards would remain an important method of data storage well into the 1980s, tapering off in the 1990s. You may be surprised that there are still punch card machines in use throughout the world, mainly used in elections for tabulating votes, though instances of them are scarce and disappearing rapidly as punch card voting machines are replaced with electronic machines.

Punched Paper Tape

Paper tape is a form of data storage similar to punch cards. In 1857, Sir Charles Wheatstone ( applied the use of paper tape to automated Morse Code transmitters. The tape had two rows, one representing the Code's dot place and the other its dash. Messages could be encoded onto the tape and fed into the transmitter, which would automatically tap out the message across the telegraph line.

In 1874, Jean-Maurice-Émile Baudot refined the use of paper tape in telegraph transmission by inventing a new encoding method dubbed Baudot Code ( The code consisted of five holes per row, allowing any one of 32 unique characters to be encoded (the system was binary). This was a huge improvement in efficiency. Eventually, paper tape was expanded to six holes (allowing 64 unique values) and then eight (for 256 unique values). This was ideal for use in computers, and it became an inexpensive high-density form of data storage from the late 1930s (when the first modern computers were being devised) well into the 1970s until floppy disk technology became prevalent.

Mechanical Storage: Patch Panels

Patch panels are effectively another form of storage, and were widely used to control the operation of a punch card machine. A patch panel consisted of a square plate with a matrix of holes. Wires were inserted between holes to make connecting paths. When the patch panel was inserted into a punch card machine, it created connections between different components or mechanisms inside the machine that would cause the machine to operate one way or another. In that regard, patch panels could be considered programs in that they told the machine how to operate.

Core Memory

IBM invented core memory in 1952 (, which would prove to be one of the most important inventions in computing. Core memory was one of the earliest forms of internal computer storage. Core memory, as the name implies, is made up of a grid of hundreds or even thousands of little ferrite rings, or cores, that look like donuts. Each ring or core can hold exactly one bit of information (on or off, one or zero.) In a typical core memory, each core has three wires strung through it: one vertically, one horizontally, and one diagonally (called the "sense" wire). Each wire is strung through a single row or column of cores.

To access an individual core, the proper horizontal and vertical wires are selected, and a half current is sent through each wire. At the intersection where these wires meet, both currents going through each wire add up to a full current, which is enough to place a charge on that one core (and that core only), which effectively results in 1 being written to that core. To read the core, the diagonal "sense" wire is used. A pulse is sent to the appropriate core using the vertical and horizontal wires, and if there were already a charge on that core, it would be leaked onto the sense wire and picked up by a circuit that would detect the charge.

The Advent of Magnetic Media: Drum, Tape, and Disk

The late 1940s saw the advent of magnetic storage devices. One of the first such devices was the magnetic drum ( This was a large barrel that had magnetic material applied in a finite number of parallel tracks around the outside of the drum. Electronic pick-ups (or heads) were then fixed over the tracks that would read/write data from/to each track as the drum spun. The drums were used to hold both data and instructions for the computer.

IBM first applied magnetic tape as a data storage medium in the 1950s ( This invention built on previous inventions that recorded audio magnetically to steel wires or magnetic tape strips (Editor's note: see

Engineering Research Associates developed hard disk technology in the early 1950s ( It built on the work of magnetic drum and tape storage technology but instead used large, flat disks coated with magnetic material. The advantage of disks over drums was that disks could hold more data in less space. One of the first commercial hard disk systems was the IBM 305 RAMAC. It contained a stack of 50 disks 24" in diameter, which could hold 5 million characters in total (a huge amount of memory for 1956.) Over time, hard disks shrunk in size while simultaneously increasing in storage capacity. By 1980, a hard drive equivalent in storage capacity to the refrigerator-sized RAMAC was the size of a shoebox.

In the 1960s, removable disk packs were invented to increase data storage. Instead of being limited to the total capacity of a fixed disk drive such as the RAMAC, removable disk packs would allow a virtually unlimited amount of data to be stored. Disk packs could be mounted into a disk drive and used until they reached capacity, then removed and replaced. Disks could be stored until their data was required later.

In 1970, IBM invented a new form of disk that was floppy instead of rigid like the disk packs, thus the floppy disk was born. The floppy disk was initially intended to be a way to transport operating system updates to mainframe computers, but eventually it found its way into practical use as a removable and more portable storage media because it was cheaper and easier to manufacture than rigid disks. The original floppy disks were 8 inches square. In the mid- to late-1970s, 5.25-inch floppy disks were introduced, and in 1981 Sony invented the 3.5-inch disk format. Although the outer shell of the 3.5-inch disk is actually stiff, the magnetic media inside is still floppy, and thus it continued to be called a floppy disk (although some people nicknamed them stiffies.) Other floppy disk formats were invented in the early 1980s including the 3-inch, 3.25-inch, and even 2-inch. The Sony 3.5-inch format is the one that stuck and still has many uses today.

Tape formats also continued to evolve from the 1960s through the 1980s. Tape cartridges became a standard backup medium in the 1970s and continue to be used today. One particularly odd tape format tried to pass itself off as floppy. So called stringy-floppy was a continuous loop tape that was intended to be used as a disk drive, but never really caught on.

Optical Media: CD-ROM

Optical media first appeared in the 1970s and was brought to market by Pioneer in their first LaserDisc video players ( Audio Compact Discs or CDs soon followed in the early 1980s, and by the mid-1980s the first CD-ROM drives had hit the market. Initially, CD-ROM, as the name implies, was a read-only technology. Before writeable CDs, a hybrid technology called Magneto-Optical was invented that enabled both reading and writing. It uses optical technology to allow for extremely high-density storage, and magnetic technology to store and retrieve data.

Data Storage Oddities

If there was a format for encoding audio, someone, somewhere, probably used it to store digital data. Anyone who used a personal computer in the 1970s and 1980s probably used standard compact audiocassettes to store programs and data. But other audio formats were used as well. Some toys and games from the late 1970s and early 1980s, such as the 2-XL by Mego ( and the Omni Entertainment System by Milton Bradley ( used 8-track tapes to record data bursts along with audio tracks. The audio track would pose a question, and a data burst containing the correct answer on the same track or on an adjoining one would be decoded by the toy to check against the player's answer. Interface Age, one of the first computer magazines published in the golden age of the late 1970s, issued programs on Floppy ROM, which were actually just cheap vinyl albums that had data encoded in the audio, as with cassette tapes (

The Future of Data Storage

Magnetic and optical disk technology (and tapes for archive purposes) will continue to be the primary data storage media for some time to come, and increasingly flash RAM technologies as density continues to increase, though new inventions on the horizon in the Quantum Mechanical realm will likely usurp these technologies eventually.