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Persistent Storage Units: Usage, History, and Evolution

Information storage systems have been with us since the dawn of computing, after all, a computer is responsible for processing information stored on a medium that is stored, which we call memory. Which we divide into two different groups.

The first of this type of storage is what we call volatile memory, it is called that because despite being much faster than non-volatile memory, it loses information as soon as it is no longer supplied with electrical energy. Which leads to the need to use persistent or non-volatile storage systems, which keep the information even after being turned off, which are also called persistent storage systems.

In the beginning they were the cassette …

The cassette as a format for storing music has been with us since 1962 and already in the seventies when the first home computers appeared, it became the favorite storage format for storing programs. The reason for this is that it was excessively cheap compared to other formats.

At that time the fastest storage memory was ROM, but not everyone had access to its mass production and it could not be written to again. So the usual thing was to make use of a cassette unit connected to an audio minijack, in which the data was transmitted at a fairly slow speed.

The problem with the cassettes is that it was a sequential storage format in which it was impossible to access a specific data. So users had to dump the contents of the cassette into the system’s RAM in order to use it. A process that was tedious and required that the first home computers needed a large amount of RAM.

… And the ROMS

ROMS persistent storage cartridges

ROMS on the other hand used to store the computer’s operating system, which used to be extremely simple and contain a BASIC interpreter with a series of commands to manage it. Operating systems were not included in the cassettes due to the inability to support random access to memory. Furthermore, part of the memory addressing of computers used to be occupied by the operating system stored in the computer’s ROM.

Another use of ROMS was to store programs, although to function they required that the computer use RAM memory to store temporary variables, they became an option for the first computers and video game consoles with the aim of saving the costs of the main unit. . Although the fall in the price of RAM in 1983 led to the progressive disappearance of ROMS, its greatest advantage was that the speed of access to its data at that time was as fast as RAM and for years they continued to be used, at least up to hard drive standardization

The appearance of the floppy disk as persistent storage

Apple II Disk

The next persistent storage format to standardize was the floppy disk or floppy disk. Which was first standardized on the Apple II Disk created by Steve Wozniak months after the release of the Apple II.

What gives a floppy disk advantages over a cassette when it comes to storing data is that it is organized in the form of a disk. Hence its name of flexible disk, where its last name is due to being formed by a piece of plastic surrounded by a magnetic material. The advantage is that the data tracks are not placed sequentially but within concentric disks, making it much easier to jump from one track to another, allowing random access to the data.

The format chosen for the Apple II floppy drive was the 5.25-inch floppy, and it offered enormous performance over the competition. The programs took much less time to load and thanks to the support of random access they could be used as memory for the programs and stored inside data files created by the user. Advantages that made the entire corporate market adopt this format and came standard with the first IBM PC

Its storage capacity? Barely 160 KB of information, but it was much more than what could be stored in the RAM of a system of the time, however the floppy disk would undergo an evolution that would further increase its storage capacity, as well as its portability.

The 3.5 inch floppy disk


During the generation of 8-bit computers, the cassette became what separated low-cost home computers from those designed for the professional market, but already in the 16-bit computer, things changed and floppy disks became standardized. 3.5 inches. Since these ended up being the standard of several 16-bit systems and not only of the PC, although each of them with its different file system.

Thus the 3.5-inch floppy, which was derived from a SONY design, was used not only by the PC, but also in systems such as the Commodore Amiga, the Atari ST, and the Apple Macintosh. We owe it to its standardization thanks to its smaller size and the fact that it can store up to 720 KB of memory per disk.

At the end of the 80s the second version of the standard appeared, which made use of modulated frequency to double its amount of data. From 720 KB to 1440 KB or 1.44 MB. Format that was the last standard format in PC, despite the existence of formats such as Zip from Iomega, which offered 100 MB of persistent storage, but was never standardized.

The hard drive, the storage format persists older

If there is a storage system that has survived all this time, it is the hard drive. Where, as with floppy disks, its origin dates back to long before the appearance of the personal computer. Specifically, in a unit as big as a room called IBM 350 and christened by Big Blue as RAMAC, an acronym that stands for Random Access Method of Accounting And Control. His capacity? Only 5MB of storage despite having drives as big as a fridge.

The first IBM PC that was launched in 1983 did not bring with it a hard disk, we owe that honor to the XT PC, which was an improved version of the first IBM PC, where the 8088 had been replaced by an 8086 and a Standard hard disk with a capacity of 10 MB, an innovation that gave IBM the professional market of the time, since the hard disk not only offered a persistent method of large size for the time, but also one that was fast enough to to be able to do without the ROMS that included the first systems.

Since then the hard disk has been an integral part of the PC and although solid memory formats have recently appeared, the low cost per stored byte means that it continues to be used today, even after 30 years.

Hundreds of MBs of persistent storage with CD-ROM


The optical format was initially intended to store and play music. Its greatest advantage was that it allowed the greatest amount of information to be encoded without data loss and any track could be chosen directly. The Compact Disk became the music standard in its own right. Without the wear and tear problems of vinyls.

The CD-ROM, which was the data version of the Compact Disk, appeared as standard in 1984, but took years to standardize for various reasons. The first reason was the inability to write data as it is a read-only format. The second was that the first units were massive in size and the third was that there were no processors powerful enough to take advantage of it.

Magnavox Announcement CD-ROM

CD-ROM drives use a laser to read the encoded binary data on the optical disc. Thanks to the use of the laser it is possible to store the data using very little space compared to other reading methods, which means that they have a large amount of information per area compared to

Its standardization occurred in the 90s, where the storage capacity of floppy disks became a nuisance. The most veteran of the place will remember installations of not a few, but dozens of floppy disks to carry out an installation. As time went by, CD-ROM readers became standardized and their cost ended up being so cheap that all PCs had one.

DVD, the ultimate commercial persistent storage drive

Persistent DVD storage

The Digital Video Disk, later known such as Digital Versatile Disk. was born to solve one of the problems of the CD-ROM, the capacity to store an entire movie and to good quality in order to replace VHS tapes.

This was achieved by using a narrower type of laser, increasing the storage capacity from 650MB to 4700MB of storage for its single-layer version and 8.5GB for the two-layer version. Which led to video games for consoles and PC eventually adopting this format as the standard for years. Your demise? It has been due to the emergence of content distribution over the internet, and it is that the network of networks has become the largest persistent storage system in the world.

The DVD had a successor in the form of Blu-ray, which had 25 GB discs, but in exchange for having a very slow access speed. Due to this, its version for data never took off as a storage format. The Internet had become a more convenient technology, both for storing programs and data for the user.