The memory hierarchy
ROM (Read-Only Memory)
This is a computer’s non-volatile memory. The data stored here can only be read and no longer modified. All the data remains secure even when the energy supply is turned off.
BIOS-ROM (BIOS – Basic Input/Output System)
The BIOS contains the control program (firmware) to start the computer. This program first looks for errors, then loads the boot loader (initial program) and afterwards starts the operating system.
EPROM (Erasable Programmable Read-Only Memory)
The data can be deleted using ultraviolet (UV) light. Afterwards new data can be written to the EPROM.
Robotron K0410 EPROM reader/writer, 1980
Price: 3,115.50 GDR marks
This device was operated on a PBT4000 computer and used for programming EPROMs. In addition, the contents of the EPROM could be deleted using the integrated deletion chamber. The storage capacity of the U555C EPROMs (left) it used was 1 KB.
Facts & figures:
The neuralyzer in the film Men in Black extinguishes memories with a flash of light and is reminiscent of a device for deleting EPROMs.
IBM 3350 hard drive, 1975
IBM introduced the IBM 3350 magnetic disk storage device in 1975. The hard drive was exceptional because of its high reliability and storage density. The storage capacity was roughly 635 MB per unit.Price at market launch: 62,500 US dollars
Hard disk drives consist of stacks of magnetizable disks. The rotating disks are read and written to with the aid of a moving read/write head. Hard disk drives can be installed inside the computer case or connected to it as an external device.
Unlike volatile memory, such as conventional RAM, hard drives are classed as mass storage: data storage systems that permanently secure large amounts of data. Mass storage can be subdivided into mechanical, magnetic, magneto-optical, optical and flash storage systems – it also includes all external forms of storage.
Facts & figures:
The first commercial computer with a hard disk drive, the IBM 305 RAMAC, was launched in 1956. Its hard drive weighed 1 tonne, its storage capacity was roughly 5 MB.
If we assume a flea weighing 1.25 mg equals 1 bit, then 1 byte (8 bits) would be equal to 10 mg. Accordingly, the 5 megabytes that this hard drive could store would roughly correspond to an emperor penguin (50 kg).
RAM (Random-Access Memory)
This is the computer’s working memory or main memory. It is linked to the processor by fast data channels. Unlike ROM, data can not only be read from RAM, but also written to it. RAM is volatile storage because the data is only secure while energy is available.
CMOS-RAM (CMOS – Complementary Metal-Oxide-Semiconductor)
Current computer settings (time, date and storage details) are kept in CMOS-RAM with the aid of a battery. If the battery runs out, the data is reset to the default values.
DRAM (Dynamic Random-Access Memory)
This is the simplest, slowest and cheapest memory. The storage element is a capacitor, and storage in the DRAM memory cell is performed by subjecting it to a charge. The charge can be read or written with the aid of a switching transistor.
SRAM (Static Random-Access Memory)
This kind of memory is very complex. As a result, it can work at very high speeds. In contrast to DRAM, SRAM is roughly one hundred times faster and does not need to be “refreshed”. That is why SRAM is commonly used in processors as cache memory.
Magnetic core memory block, circa 1970
Magnetic core memory is regarded as the precursor of present-day RAM. It consists of wires and magnetizable ring cores. Each ring core stores 1 bit when current flows.
Magnetic core memory, circa 1965,
Sharp PC-E500, 1989
The Sharp PC-E500 is a pocket computer with built-in programs, among other things, for mathematics, physics and statistics. The working memory could be upgraded from 32 KB to 256 KB with memory expansion cards. This enabled the storage of user’s own programs. The device could be expanded by a printer or cassette drive with the aid of a special interface.
This is buffer memory that is directly integrated in the processor. All required data is loaded into the cache first to ensure the computer does not have to collect each data element individually. That enables fast data access.
Intel i486SX processor, 1989
The 32-bit i486 processor was the first Intel processor with integrated cache memory.
Facts & figures:
A cache is “hot” when it is working at peak efficiency, i.e. it is full. If that is not the case, the cache is regarded as “cold”, for example, after starting up, because it does not yet hold any data and it has be painstakingly loaded.
The best known cache is probably the read cache used by search engines: a web crawler searches through the World Wide Web looking for new or changed web pages, which it uploads into the search engine cache. This data is regularly used to compile different indices which a search algorithm runs through to find the appropriate web pages in reply to a user request.
CPU REGISTERS (CPU – central processing unit)
This is an internal memory cell in the processor. Depending on the respective model, the registers have a storage capacity of 8 to 512 bits and are used as internal arithmetic storage. The number of CPU registers depends on the CPU architecture.
Jugend + Technik magazine, September 1989
The GDR magazine focuses on the development of the 4-megabit chip. You will find the text extract in our Multimedia Station.
If we assume a flea weighing 1.25 mg equals 1 bit, then 1 byte (8 bits) would be equal to 10 mg. Accordingly, the 80 bytes that fit on a punched card would roughly correspond to a May bug (approx. 0.8 g).
Punch by punch
Hermann Hollerith (1860–1929), circa 1888
Advertisement on the advantages of punched card technology
The punched card at the centre of technological tools
More on the subject
“In very large firms, in some cases already here in Austria too, completely electric bookkeeping is in use that works on the basis of the punched card process invented by the American engineer Dr. Hermann Hollerith. This Accounts Department works completely automatically; nothing needs to be written down any more.”
Der Morgen. Wiener Montagblatt, 12 March 1928
“Working with the machine is crucial here. The key element – namely, the placing of the weights that perforate the card at the right place – is the work done by the girls, which is in fact mentally very tiring. Usually graduates of technical or commercial schools are employed; for a monthly salary of roughly 800 crowns one of these girls works seven hours a day, during which she is able to furnish 3,000 cards with the appropriate perforations.”
Prager Tagblatt, 19 January 1930
IBM 26 key punch, 1950
The IBM 26 Key Punch was used for punching numerical and alphabetical data on a punched card. The punched card feed and punched card store worked automatically and fast. The machine could also produce punched card duplicates.
IBM punched card and manual verifier for punched cards
A manual punched card verifier was used to check the precision of a card punch. A card would be punched by the respective machine for that purpose. Then it would be laid on the verifier to determine whether there were any deviations between the punched perforations and the black rectangles.
“The punched card is now the basis for further mechanical manipulation…
Therefore, ‘Catholics’, ‘Czechs’, ‘Germans’ and ‘Jews’ are automatically sorted and at the same time also counted by the machine.”
Prager Tagblatt, 19 January 1930
… from data processing to data abuse
Deutsche Hollerith-Maschinen Gesellschaft mbH (DEHOMAG) was founded in 1910. DEHOMAG machines were used to separate the Jewish population at the time of the Nazi regime. Information about people’s affiliation to the Jewish religion was collected and analyzed in the 1933 and 1939 censuses. Later, this was used to organize the transports to the concentration camps.
(punched cards as physical reproductions):
Record card of a concentration camp prisoner with the mark “Hollerith recorded”, 1944
Reproduction: Arolsen Archives / 220.127.116.11 / 5803453
Prisoner record cards were used to collect personal data in concentration camps. The pictured card comes from the concentration camp at Auschwitz-Birkenau. The Hollerith machines were deployed there to keep track of the constantly changing prisoner numbers. After processing by the machine the card received a stamp in black ink stating “Hollerith recorded”.
Punched card from a maternity hospital, 1942
Reproduction: Stiftung Deutsches Technikmuseum Berlin
This punched card was used for the statistical registration of pregnant women in maternity hospitals or in maternity homes for female forced labourers. Various sub-characteristics are found on the punched card, including details of “racial appearance”.
IBM D11 tabulating machine
The IBM D11 tabulating machine was used for data evaluation in concentration camps.
IBM 082 Card Sorter, 1949
This machine was used to sort punched cards by evaluating the punched numeric or alphabetical data. It could process some 39,000 punched cards in an hour.
Data protection and data security
Data protection has been regulated by law since the 1970s in Germany. Its goal is to protect personal data against misuse. Data protection is closely bound up with personal rights and the right to privacy. The right to informational self-determination applies in Germany. This means that everyone should be able to decide which data they make available.
Data security, on the other hand, covers all the technical factors that serve to protect data, for example, against data loss or unauthorized access.
Who is listening in?
Virtual assistants are becoming increasingly popular. Nevertheless, they constitute a data protection challenge. They send data to their respective operator, which could then be misused. If you are unable to make do without Alexa, Siri & Co. then you should at least ensure the device is only turned on explicitly when it is used.
“It is not precisely defined when the assistant listens and what happens with the data… Either you trust the manufacturers and use their services or you do not trust them and therefore do not use them.”
Prof. Sebastian Schinzel, IT security expert, in the Westfälische Nachrichten, 8 April 2019
Statistics on data misuse in the Internet
Between January 2013 and February 2017 over 44 million stolen data sets were registered in Germany alone.
© Epiq Systems
Use of virtual assistants
© Ipsos GmbH
My Friend Cayla doll with removed transmitter
Germany’s Federal Network Agency classified the Hello Barbie and My Friend Cayla dolls as espionage devices in 2015 and 2017 respectively. For that reason, the doll’s transmitter had to be made inoperable for the exhibition.
“Hello Barbie functions in a similar way to the voice recognition software in many smartphones: a microphone located in the doll’s neck records everything that Barbie’s playmates say.”
Stern, 9 November 2015
“A Barbie with Wi-Fi is the end of childhood.”
Die Welt, 22 April 2015
“Destroy this doll”
Zeit online, 17 February 2017
“The first Barbie doll gave many women poor body image. The next generation could speak and said things like ‘Mathematics is difficult, let’s go shopping instead.’ The third doll, Smart Barbie, listens to what little girls tell her – Barbie records all these secrets and passes them on to Mattel.”
Gerd Gigerenzer in Tagesspiegel, 12 January 2019
Data storage yesterday, today and tomorrow
Mechanical data storage
These media enable data to be stored or written by mechanical means. They can usually be recognized by indentations or bumps in the material.
Inexpensive Low storage capacity
Readable visually or by machine Can only be written to once
If we assume a flea weighing 1.25 mg equals 1 bit, then 1 byte (8 bits) would be equal to 10 mg. Accordingly, the 80 bytes that fit on a punch card would be roughly the equivalent of a May bug (approx. 0.8 g).
Facts & figures:
Konrad Zuse used special mechanical memory in his Z1. It consisted of several strips of metal lying on top of one another. It was possible to represent the data in memory with the aid of these strips and a number of pins.
Mechanical memory of the Z1 computer system
Reproduction between 1987 and 1989
ORGACARD punched card for recording data
The data is entered by hand and evaluated by the machine.
Leporello punched tape for an Intelec 8 with the program for a text editor, circa 1980
Processing a punched tape program on the KRS 4200 computer
Magnetic data storage
The data media are read and written to with the aid of a read/write head. They consist of a magnetizable material or have a coating of this kind.
Reusability Slow access time
High storage capacity Sensitive to external influences and magnetic fields
Magnetic tapes are still used today for long-term data archiving because of their higher durability and low price.
Storage of magnetic tapes for the UNIVAC 1100/80, circa 1977
Facts & figures:
Magnetic tape was used for the first time in 1951 as external storage for the UNIVAC computer.
Telefunken magnetic tape
Data is only secure on magnetic tape if the tape is stored correctly. If the air humidity is too high, an oxidation layer forms on the magnetic tape spool that can also affect the tape itself. Poor or excessively long storage of the magnetic tapes results in the storage medium losing its magnetism, which leads to data loss.
LCR-C cassette drive, 1975
The LCR-C cassette drive was often used by home users in the 1980s to store data and programs on a cassette (Datasette).
Cassette (Datasette) for the KC 85 with software, circa 1984
VEB Mikroelektronik Wilhelm Pieck Mühlhausen
Minidiskette container with diskettes by VEB Kombinat Robotron Büromaschinenwerk E. Thälmann Sömmerda, 1988
If we assume a flea weighing 1.25 mg equals 1 bit, then 1 byte (8 bits) would be equal to 10 mg. Accordingly, the 80 kilobytes that could be stored on an 8-inch diskette in 1971 would roughly correspond to a hedgehog (approx. 800g) and the 1.44 megabytes that fitted on a 3.5-inch diskette in 1987 would be the equivalent of a medium-sized dog (approx. 14 kg).
Sonny Digital Data Storage, circa 1995
Digital Data Storage was developed by Sony and HP in 1989. It was used to store and archive data. The storage capacity was 4 GB.
Iomega clik!, 2000
Iomega clik! was launched on the market in the year 2000 and was used as data storage for digital cameras and the Hip-Zip MP3 player. They cost 24 deutschmarks. The storage capacity was 40 MB.
Optical data storage
Data media that are written to or read with the aid of light.
Reusability Slow access times
High storage capacity Sensitive to external influences
The first CDs (Compact Discs) were developed from 1979 onwards by Sony and Phillips. The goal was to supersede the analogue music storage medium of the vinyl record. The storage capacity of the CD was 650 MB. Writers became available during the 1990s that enabled users to write their own data onto CDs or DVDs.
If we assume a flea weighing 1.25 mg equals 1 bit, then 1 byte (8 bits) would be equal to 10 mg. Accordingly, the 650 megabytes that can be stored on a CD would be the equivalent of a fully grown elephant (approx. 6,500 kg).
Facts & figures:
The first music album published on CD was The Visitors by ABBA (1982).
The name of the disc authoring program NERO Burning ROM is a German pun. It does not only describe the software’s function of writing or “burning” discs, but also refers to Nero, the Roman emperor who is said to have fiddled while Rome burned. In German the city’s name is spelled Rom.
According to legend, the size and playing time of the CD were defined by the music preferences of Norio Ōga, Sony’s vice president at the time. As a trained opera singer he wanted to be able to listen to Beethoven’s Ninth without changing discs. In the 1951 version conducted by Wilhelm Furtwängler the symphony lasts exactly 74 minutes.
Illustration on this subject:
Screenshot of the NERO Burning ROM program
© Nero AG
ABBA, The Visitors, 1982
Pocket CD-RW, 1990s
Pocket or mini CDs were mainly used to store music or photos. Their storage capacity is 210 MB, which corresponds to roughly 23 minutes of playing time.
Magneto-optical data storage
This technology uses media that can be written to magnetically and read optically. Their material or storage layer is non-magnetizable at room temperature, but can be magnetized after heating with the aid of a laser. It is a comparatively long-lived form of data storage…
Fujifilm 5.25-inch, 1991
Rewritable magneto-optical disc with a storage capacity of 650 MB.
Flash memory and the cloud
Flash memory involves electronic storage media that can be easily and quickly written to. They can be deleted and filled with new data as often as necessary. The data is “stored” on microchips for this purpose. This kind of memory includes, among others, SD cards (Secure Digital Memory Card), USB flash drives (Universal Serial Bus) and SSD hard disk drives (solid-state drive).
The cloud is based on online storage. Servers are made available for this purpose by various service providers. Cloud storage has the advantage that large amounts of data are accessible at any time and anywhere as long as the user has Internet access. There is the risk of data loss, however, if the service provider goes bankrupt…
If we assume a flea weighing 1.25 mg equals 1 bit, then 1 byte (8 bits) would be equal to 10 mg. Accordingly, one terabyte that can normally be stored on a memory stick would be the equivalent of the total weight of the Eiffel Tower (approx. 10,000 tonnes).
Facts & figures:
The name flash probably emerged at the Toshiba development lab. One of the employees was reminded of the flash of a camera during the memory deletion process.
Israeli inventor Dov Moran is said to have come up with the idea for the USB flash drive in 1998 because of a defective laptop. Since the computer on which the only copy of his company presentation was stored would not run, he had the idea for a universal flash storage drive for your trouser pocket that would be usable on every computer via the USB interface. His firm then developed the DiskOnKey technology.
Exhibits on this subject:
IBM DiskOnKey USB flash drive, 2000
The flash drive was developed by Dov Moran’s M-Systems company and sold to IBM. The exhibit is one of the first USB flash drives ever produced. Its storage capacity was only 8 MB.
Olympus memory cards, circa 1997
These cards were used as memory in digital cameras and keyboards. The storage capacity of the exhibited cards is about 4 and 16 MB.
Bloomberg Business Week: Put Your Head in the Cloud, 2011
The cover of the US business magazine highlights cloud storage.
Innovative storage methods – for example, DNA
DNA (deoxyribonucleic acid) is used to carry the genetic information of every living thing and is therefore one of the world’s oldest storage media. Any sequence of data can be encoded in artificially produced strands of DNA. Its durability and data density far exceed those of current storage media. Thus, for example, over 200 petabytes of data could be stored for tens of thousands of years in one gram of DNA. At present, however, the complexity and cost of this technology are too high for mass application.
If we assume a flea weighing 1.25 mg equals 1 bit, then 1 byte (8 bits) would be equal to 10 mg. Accordingly, the 200 petabytes that can be stored in one gram of DNA would be the equivalent of the estimated weight of the whole of Berlin (approx. 2 billion tonnes).
“This one capsule of DNA contains as much data as an entire Facebook data centre.”
Emily Leproust, cofounder and CEO of Twist Bioscience, San Francisco
Illustration on this subject:
DNA – data storage medium of the future?
Facts & figures:
The first successful data storage attempt using synthesized DNA did not only archive a photograph of the research institute involved, but also the paper on “Molecular Structure of Nucleic Acids”, a text file of Shakespeare’s sonnets and an MP3 file of Martin Luther King’s “I Have a Dream” speech.
Using the present method, it would be possible to store 100 million hours of high-definition video in a coffee cup full of DNA. In 2019, roughly 400 hours of video material was uploaded to YouTube every minute. That is already the equivalent of a little over two coffee cups full of DNA data storage per year.
Will be become cyborgs with built-in data storage?
Oliver Waack-Jürgensen, member of the Berlin Cyborg Club, walks with the aid of two artificial knees and one artificial hip. During his next operation he wants the surgeon to install a mobile charging device in his hip implant, a data storage unit and a Wi-Fi router…
What would you like to “upgrade”?
Illustration on this subject:
Neil Harbisson and Steve Mann show their cyborg passes, 2015
© Neil Harbisson, Steve Mann / Wikimedia commons, License: CC BY-SA 4.0
Quotation on this subject:
“Psychologically speaking, most of us are already cyborgs anyway. We can’t live without our smartphones any more. In 30 years it will be normal for everyone to have these kinds of implants in their bodies.”
Neil Harbisson is the first state-recognized cyborg (combination of human and machine). Colour-blind Harbisson can “hear colours” thanks to an antenna and microchip in the back of his head.