MB

(1) (MB) (MegaByte) One million bytes (1,000,000 bytes or 1,048,576 bytes). See mega and space/time.

(2) (MB) (MotherBoard) On references to basic hardware components, MB often means motherboard or mainboard.

(3) (Mb) (MegaBit) One million bits (1,000,000 bits or 1,048,576 bits). In communications, mega typically refers to 1,000,000. In storage, mega typically refers to 1,048,576. Lower case "b" for bit and "B" for byte are not always followed and often misprinted. Thus, Mb may refer to megabyte. See mega and space/time.

A Whopping Hundred Megabytes!

Back in the 1970s, all these 14" disks held in total was 100 megabytes. Today, that much platter space would hold 10,000,000 megabytes. (Image courtesy of The Computer History Museum, www.computerhistory.org)

---

(unit)

MB - (Or "Mb") megabytes or megabits. When referring to the size or data transfer rate of a storage device which is accessed in multiples of eight bits (e.g. RAM, hard disk) this almost certainly means megabytes, but when referring to the data transfer rate of a communications system it probably means megabits. Some years ago, it is claimed, "MB" always meant megabytes and "Mb" meant megabits but recently this useful distinction has been lost.