C-D, or Compact Disc, is a digital optical disc storage format that was introduced in the early 1980s. It was primarily designed to store and play music, but later versions were developed to hold data, making it a versatile medium for various types of information. The standard capacity of a CD is about 700 megabytes, which can hold approximately 80 minutes of audio. The technology behind C-D involves a laser reading the encoded data on the disc's surface. This data is stored in the form of tiny pits and lands, which represent binary information. Over the years, C-Ds have been largely replaced by digital downloads and streaming services, but they remain a significant part of music and data history, influencing formats like DVD and Blu-ray.