UNIT DEFINITION ABBREVIATION
bit The computer term “bit” comes from the phrase “Binary DigIT,” which is different than that thing you put around a horse’s mouth. A bit is a single digit number in base-2 (a zero or a one) and is the smallest unit of computer data. A full page of text is composed of about 16,000 bits.It is important not to confuse bits with bytes. Both are used to measure amounts of data, but it takes eight bits to make one byte. The most common area where bits are used intstead of bytes is in measuring bandwidth (in bits per second). Why? Probably because it makes your Internet connection sound faster than it really is. b
Byte A byte is a unit of measurement used to measure data. One byte contains eight binary bits, or a series of eight zeros and ones. Therefore, each byte can be used to represent 2^8 or 256 different values. B
Kilobyte A kilobyte is 2 to the 10th power, or 1,024 bytes.”But doesn’t ‘kilo’ means one thousand?” you ask. Well yes, but in the computer world, certain rules and guidelines don’t have the same influence they do in other areas of life. Just ask any computer programmer. A kilobyte is technically 1,024 bytes because it is measured by 2^10, which equals 1,024. However, kilobytes are often estimated as 10 to the 3rd power, or 1,000 bytes. While this makes it easier to add kilobytes together, estimating can throw off larger measurements. This is because 1,024 kilobytes equal one megabyte, 1,024 megabytes equal one gigabyte, and so on.Most small files on your computer are measured in kilobytes. For example, thumbnail images might use only 5 to 10KB of space. A larger 900×600 pixel JPEG image can take up 250KB of space. Text files are often less than 1KB. Most documents you save on your computer should be between 1 and 1,024KB. Anything larger than 1,024KB is measured in megabytes. KB
Megabyte A megabyte is 2 to the 20th power, or 1,048,576 bytes. Large computer files are typically measured in megabytes. For example, a high-quality JPEG photo from a 6.3 megapixel digital camera takes up about 3MB of space. A four minute CD-quality audio clip takes up about 40MB of space and CDs can hold up to 700MB of space. MB
Gigabyte A gigabyte is 2 to the 30th power, or 1,073,741,824 bytes.  Hard drive sizes are typically measured in gigabytes, such as a 160GB or 250GB drive. The term gigabyte is often often abbreviated as simply a “gig” in speech. For example, if you have a 250GB hard drive, you could say, “I have 250 gigs of disk space.” The prefix “giga” comes from the Greek word “gigas,” meaning giant. GB
Terabyte A terabyte is 2 to the 40th power, or 1,099,511,627,776 bytes. While today’s consumer hard drives are typically measured in gigabytes, Web servers and file servers may have several terabytes of space. A single 500GB hard drive can also be called a half-terabyte drive.The prefix “tera” comes from the Greek word meaning “monster.” So, if you have a 500GB hard drive, you could say you have half a monsterbyte of disk space. If nothing else, it sure sounds impressive. TB
Petabyte A petabyte is 2 to the 50th power, or 1,125,899,906,842,624 bytes. Since even the largest hard drives are measured in terabytes, petabytes are only used to measure the storage space of multiple hard drives or other collections of data. And no, “petabyte” is not what you do to make a byte purr. PB