WHAT ARE UNITS OF MEASURE FOR
DIGITAL INFORMATION?
A bit is a binary digit, the smallest increment of data on a computer. A bit can hold only one of two values: 0 or 1, corresponding to the electrical values of off or on, respectively.
Because bits are so small, you rarely work with information one bit at a time. Bits are usually assembled into a group of eight to form a byte. A byte contains enough information to store a single ASCII character, like "h".
A kilobyte (KB) is 1,024 bytes, not one thousand bytes as might be expected, because computers use binary (base two) math, instead of a decimal (base ten) system.
Computer storage and memory is often measured in megabytes (MB) and gigabytes (GB). A medium-sized novel contains about 1MB of information. 1MB is 1,024 kilobytes, or 1,048,576 (1024x1024) bytes, not one million bytes.
Similarly, one 1GB is 1,024MB, or 1,073,741,824 (1024x1024x1024) bytes. A terabyte (TB) is 1,024GB; 1TB is about the same amount of information as all of the books in a large library, or roughly 1,610 CDs worth of data. A petabyte (PB) is 1,024TB. Indiana University is now building storage systems capable of holding petabytes of data. An exabyte (EB) is 1,024PB. A zettabyte (ZB) is 1,024EB. Finally, a yottabyte (YB) is 1,024ZB.
Many hard drive manufacturers use a decimal number system to define amounts of storage space. As a result, 1MB is defined as one million bytes, 1GB is defined as one billion bytes, and so on. Since your computer uses a binary system as mentioned above, you may notice a discrepancy between your hard drive's published capacity and the capacity acknowledged by your computer. For example, a hard drive that is said to contain 10GB of storage space using a decimal system is actually capable of storing 10,000,000,000 bytes. However, in a binary system, 10GB is 10,737,418,240 bytes. As a result, instead of acknowledging 10GB, your computer will acknowledge 9.31GB. This is not a malfunction but a matter of different definitions.
1 kilobyte (KB) 1,024 bytes
1 megabyte (MB) 1,048,576 bytes
1 gigabyte (GB) 1,073,741,824 bytes
1 terabyte (TB)1,099,511,627,776 bytes
1 petabyte (PB)1,125,899,906,842,624 bytes
