Understanding Data Storage

Digital data storage in one form or another has been with us since the early eighteenth century. The very first digital data storage was the punched card, invented by Basile Bouchon in 1725 for storing data to automate various manufacturing processes in textile looms. Modern data storage has its roots in the fifties, when magnetic tape media became widespread in industrial and commercial applications. The very first hard disk drive was the IBM 350, introduced in 1956. Larger than a refrigerator, it provided a storage capacity of 3.75 megabytes across dozens of 24-inch disk platters. Today, digital storage is more often measured in gigabytes and terabytes. The following takes a look at the digital storage capacities and their various applications.

Bits and Bytes

A single byte is composed of eight bits. A bit is the smallest unit of information used in computing and communications, and it may only have one of two values. These values are typically represented by the symbols ‘0’ and ‘1.’ A bit is short for binary digit. A byte represents a single character in most languages which use an alphabetic writing system, such as Latin, Cyrillic, Arabic or Hebrew. For example, a basic text file consisting of ten characters (including hidden ones such as spaces and paragraph marks) will require exactly ten bytes of digital storage space. Characters from more complex writing systems, such as Chinese, Japanese or Korean, require two or more bytes each, depending on the particular character encoding used.


One binary kilobyte is equal to 1024 bytes, despite the fact that the prefix kilo- means one-thousand. A kilobyte may also be used to describe 1,000 bytes, depending on the context. However, when talking about data sizes and capacities, a kilobyte usually refers to the former. A single kilobyte is roughly equivalent to a 100-word basic text document. The average compressed picture size for a photo with a resolution of around 1024×768 is typically around 250 kilobytes in size. Early floppy disks had a capacity of 720 kilobytes.


A megabyte is 1024 kilobytes. Megabytes are commonly used when referring to the size of digital audio tracks (MP3s), large images and smaller program installations. For example, a typical MP3 music track using high-quality compression is usually between 4-5 megabytes in size. Large compressed images taken by today’s 12-16 megapixel cameras typically range in size from 3 to 5 megabytes. Five MB of data storage is enough to store the entire works of Shakespeare in plain text format. Later floppy disks had a capacity of 1.4 megabytes, while CD-ROMs provide 720 MB.


A gigabyte is around a billion bytes or 1024 megabytes. Today’s data storage capacities are most often measured in gigabytes with a typical modern hard drive providing upwards of 500 gigabytes of storage space. The average modern video game installation takes up between five and fifteen gigabytes due to huge amounts of multimedia resources including high-definition texture files, audio tracks and video content. A single-layer DVD disk offers a capacity of 4.3 GB, while a single-layer Blu-ray disk provides 50 GB. Dual-layer disks provide double the capacity, and double-sided dual-layer disks provide quadruple the capacity.


In the last few years, home computing has stepped into the terabyte realm with many hard disks offering between one and three terabytes of data storage space. A single terabyte is equal to 1024 gigabytes, or over a trillion bytes. This might sound a lot, but as programs, games and operating systems continue to get larger, our storage devices need to grow to be able to accommodate them. A single terabyte provides enough storage space for around two-hundred compressed high-definition digital videos, or approximately seventeen-thousand hours of MP3 audio. Holographic versatile disks, expected to be the successor to Blu-ray disks, provide a capacity of up to six terabytes.


1024 gigabytes is a petabyte. Although rarely heard of in everyday computing, the world of demanding data storage applications is rapidly heading towards the petabyte realm. Currently, the entire digital storage capacity consumed by the Internet is around ten petabytes, and this figure is constantly growing. All material ever printed or stored on digital storage devices is estimated to run into several hundred petabytes.

Exabytes and Beyond

Beyond petabytes, exabytes and larger digital storage measurements are largely a thing of curiosity rather than practical application. To provide a couple of statistics, it is estimated that the total volume of data generated every year is around two exabytes, or 1024 petabytes. Beyond exabytes are zettabytes and then yottabytes, though these currently have absolutely no practical application as of yet.

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