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Thursday, 5 January 2012

What Is a Computer Megabyte ?

The prefix "mega" -- from the Greek "megas", meaning "large" -- means "one million" so, in computing terminology, "megabyte" (abbreviation MB) is often used, loosely, to mean one million bytes. However, computer memory must increase by binary or base two increments, so one megabyte is actually 2^20, or 1,048,576 bytes.

Bits And Bytes

In computing terms, the smallest unit of information is known as a binary digit, or "bit." A bit represents the amount of data obtained by asking a yes-or-no question and can take one of two values, 0 and 1. A series of eight, adjacent bits, is called a byte. Each byte represents a particular letter, number or special character. Primary and secondary computer storage is capable of storing millions, billions or even trillions of bytes, so for the sake of convenience storage is typically measured in megabytes, gigabytes or terabytes.

Primary And Secondary Storage

The fact that random access memory and hard disk storage are both measured in megabytes can cause confusion, especially among novice computer uses. RAM is a volatile form of storage -- its contents are erased when the power to the computer is switched off -- which is used to temporarily store the programs and data the computer is currently using. Hard disk storage, on the other hand, is non-volatile and is used to store programs and data on a more permanent basis. A computer typically has much more -- possibly 100 times more -- hard disk storage than RAM.

Historical Context

The first hard disk for microcomputers, introduced by IBM in 1956, had a storage capacity of just 5 megabytes, but occupied the floor space required by two modern refrigerators and weighed nearly a ton. In more than five decades since, the storage capacity of hard disk drives has dramatically increased, while their physical dimensions have dramatically decreased. In October 2010, Western Digital announced a 3 terabyte hard disk drive in the standard, 3.5-inch form factor.

Megabytes Vs. Megabits

The megabyte (abbreviation MB) should not be confused with the megabit (abbreviation Mb), which is a unit of data equivalent to 1,048,576 bits or, if expressed per second, a unit of data transfer speed, or bandwidth, across a network. The upload and download speeds of a broadband Internet connect, for example, may be quoted in megabits per second (Mbps). Confusingly, megabytes and megabits per second can be referred to, colloquially, as "meg" or "megs", but be aware that they are, in fact, different units.

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