In a digital storage unit, data and information are measured by how much space it occupies on devices like a computer hard drive. If you discuss about storage unit with an IT specialist or executive, you might hear words like bits, bytes, megs, and gigabytes, etc.
You can get swept up in data storage jargon, especially when you’re talking about different types of storage units. Bits vs. bytes: what’s the difference? Which is larger, megabytes or gigabytes? How do terabytes and kilobytes differ? To help you digest these concepts, we have provided you with this resource.
In this section, we will describe what a storage unit is and how it varies in size from the tiny Bit (b) to the gigantic Yottabyte (YB).
The smallest unit of data in a computer is called Bit (Binary Digit). A bit has a single binary value, either 0 or 1. In most computer systems, there are eight bits in a byte. The value of a bit is usually stored as either above or below a designated level of electrical charge in a single capacitor within a memory device.
Half a byte (four bits) is called a nibble.
In most computer systems, a byte is a unit of data that is eight binary digits long. A byte is a unit most computers use to represent a character such as a letter, number, or typographic symbol (for example, “g”, “5”, or “?”). A byte can also hold a string of bits that need to be used in some larger unit of application purposes (for example, the stream of bits that constitute a visual image for a program that displays images or the string of bits that constitutes the machine code of a computer program).
In some computer systems, four bytes constitute a word, a unit that a computer processor can be designed to handle efficiently as it reads and processes each instruction. Some computer processors can handle two-byte or single-byte instructions.
A byte is abbreviated with a “B”. (A bit is abbreviated with a small “b”). Computer storage is usually measured in byte multiples. For example, an 820 MB hard drive holds a nominal 820 million bytes – or megabytes – of data. Byte multiples are based on powers of 2 and are commonly expressed as a “rounded off” decimal number. For example, one megabyte (“one million bytes”) is actually 1,048,576 (decimal) bytes.
In some systems, the term octet is used for an eight-bit unit instead of byte. In many systems, four eight-bit bytes or octets form a 32-bit word. In such systems, instructions lengths are sometimes expressed as full-word (32 bits in length) or half-word (16 bits in length).
A Kilobyte (kb or Kbyte) is approximately a thousand bytes (actually, 2 to the 10th power, or decimal 1,024 bytes).
As a measure of computer processor storage and real and virtual memory, a megabyte (abbreviated MB) is 2 to the 20th power byte or 1,048,576 bytes in decimal notation.
A Gigabyte (pronounced Gig-a-bite with hard G’s) is a measure of computer data storage capacity and is “roughly” a billion bytes. A gigabyte is two to the 30th power or 1,073,741,824 in decimal notation.
A Terabyte is a measure of computer storage capacity and is 2 to the 40th power of 1024 gigabytes.
A Petabyte (PB) is a measure of memory or storage capacity and is 2 to the 50th power bytes or, in decimal, approximately a thousand terabytes (1024 terabytes).
An Exabyte (EB) is a large unit of computer data storage, two to the sixtieth power bytes. The prefix exa means one billion billion, or on quintillion, which is a decimal term. Two to the sixtieth power is actually 1,152,921,504,606,846,976 bytes in decimal, or somewhat over a quintillion (or ten to the eighteenth power) bytes. It is common to say that an Exabyte is approximately one quintillion bytes. In decimal terms, an Exabyte is a billion gigabytes.
A Zettabyte (ZB) is equal to one sextillion bytes. It is commonly abbreviated ZB. At this time, no computer has one Zettabyte of storage. It has 1024 Exabytes.
A Yottabyte is equal to one septillion bytes. It is commonly abbreviated YB. At this time, no computer has one Zettabyte of storage. It has 1024 Zettabytes.