Introducing the UNIX Directory Tree Structure
UNIX stores information such as user data on one or more disk drives. Each disk drive typically has a capacity measured in megabytes (MB), where each megabyte is equivalent to roughly 1 million characters. For example, a 500MB disk drive could hold 50,000 documents, where each document has 10,000 characters of text. Some disk drive systems have capacities measured in gigabytes (GB) or terabytes (TB). Here is a summary of the units used to measure disk capacity.
1 KB = 1,024 characters (or bytes) (roughly 1,000)
1 MB = 1,024 KB = 1,048,576 characters (roughly 1 million)
1 GB = 1,024 MB = 1,073,741,824 characters (roughly 1 billion)
1 TB = 1,024 GB = 1,099,511,627,776 characters (roughly 1 trillion)