In this blog post, we’ll take an easy-to-understand look at the difference between analog and digital, as well as the principles behind how hard drives store and read information.
LP records that evoke a sense of nostalgia just by looking at them, videotapes crammed into the cabinet under the TV, and dozens of encyclopedias that made you feel somehow smarter when they filled your bookshelf—these items are now hard to find in everyday life. Before we knew it, most of these items began to be stored inside the computer sitting in the corner of the room—more precisely, in storage devices like hard drives or SSDs, which can store far more information in the same amount of space. However, these storage devices do more than simply hold a large amount of data. Their most significant feature is that the very method of storing information is fundamentally different from the past. This is the “digital” storage method.
So what exactly does “digital” mean? And how do hard drives store and process information? To understand this, we first need to examine the difference between analog and digital. Generally, analog refers to a method of representing quantities or values that change continuously, while digital refers to a method that uses discrete values divided into fixed units. For example, a thermometer where the red mercury column rises continuously is analog, whereas a digital thermometer that displays a numerical value, such as 37.5°C, is digital.
From the perspective of storage media, the two methods also differ. Analog storage media either store the original information as-is or convert it into a signal form that corresponds continuously to the original information. In contrast, digital storage media, such as hard disks, divide the original information into multiple discrete values according to predetermined rules and then store those discrete values. To put it simply, if the analog method is like a drawing that faithfully replicates the original, the digital method can be understood as resembling a highly intricate mosaic.
To make this a bit easier to understand, let’s consider a very simple digital representation. Imagine a sunset sky tinged with red. In this hypothetical system, we’ll assume that the sky’s color is represented using only four colors: red, crimson, orange, and yellow. We’ll also divide the entire sky into 100 small sections and assign each section one of these four colors. As a result, the sky—which was originally a continuous expanse—is divided into 100 small sections, and each section contains only one of the four colors: red, crimson, orange, or yellow. This is the fundamental concept of the digital system.
Since digital information consists of discrete values, each color can be mapped to a number. In particular, computers represent this information using binary numbers. This is because, in actual electronic devices, two states—such as “present and absent,” “on and off,” or “high and low”—can be distinguished most reliably. These are represented by 0 and 1, respectively. For example, let’s agree that red is “00,” crimson is “01,” orange is “10,” and yellow is “11.” Then, the color of each square can be expressed as a combination of 0s and 1s, and in this way, the information is converted into digital form.
If we use millions of colors instead of just four, and divide the image into tens of millions of very small sections instead of just 100, the digitally represented information can be reproduced with such precision that it is nearly indistinguishable from the original landscape.
So how does a computer distinguish whether these countless 0s and 1s represent an image, sound, or text data? The principle is surprisingly simple: by storing a marker before and after each piece of information that indicates its type. In other words, information such as “the data that follows is image data” or “image data ends here” is also represented by 0s and 1s and stored alongside the data. For example, if a system defines the start of image data as “1101” and the end as “1111,” the stored information would take the form “1101 … data consisting of 0s and 1s representing the image … 1111.”
Of course, in actual computers, this method of differentiation is much more complex and systematic. Digital information systems use various rules and formats to ensure that the patterns used to distinguish information are not confused with the actual data. Based on these principles, computer storage devices accurately store and manage vast amounts of digital information.
