The definition information for symptom substitution is provided by Stedman's. You can search our medical dictionary here. Stedman's, part of Lippincott Williams & Wilkins, provides a comprehensive line of health-science publications for healthcare professionals and medical students.
Gigabyte: A Gigabyte is approximately 1,000 Megabytes. A Gigabyte is still a very common term used these days when referring to disk space or drive storage. 1 Gigabyte of data is almost twice the amount of data that a CD-ROM can hold. But it's about one thousand times the capacity of a 3-1/2 floppy disk. 1 Gigabyte could hold the contents of about 10 yards of books on a shelf. 100 Gigabytes could hold the entire library floor of academic journals.
Usually, a gigabyte is defined as 1000 megabytes in computer storage, such as when referring to the capacity of a hard drive. For processor storage or virtual storage, however, a gigabyte is commonly defined as 1024 megabytes. This is equivalent to a 2 percent difference, so the two definitions are approximately equivalent. It takes about 3 megabytes to hold a single song and 1 megabyte to hold a picture of moderate quality.