A data element containing eight bits, or 256 distinct values. Commonly used to store a single text character. Computer data transfer rates are traditionally measured in bits, as in Mb for Megabits (millions of bits, with a lower-case "b"); whereas computer data storage is traditionally measured in bytes, as in MB, for megabytes (millions of bytes, with an upper-case "B"). 

The size of the files used and stored on computers today can be very large. Even a small image file consists of millions of bits. In order to express large amounts of data, different concepts are used instead of bits.8 bits are called 1 byte. Then, larger dimensions are expressed with expressions such as kilo, mega, giga, tera.

8 bits = 1 byte

1024 bytes = 1 kilobyte (KB)

1024 kilobytes = 1 megabyte (MB)

1024 megabytes = 1 gigabyte (GB)

1024 gigabytes = 1 terabyte (TB)

1024 terabytes = 1 petabyte (PB)

Hard disks have now reached terabyte sizes. Flash memories can be in capacities of 16, 32, 64 gigabytes etc. The space that files occupy in memory depends on many factors. For example, the size of a photo you take with your phone, the space it occupies in memory, varies depending on factors such as the quality of the photo, color depth, and recording type. So a high quality photo will take up more space. Music and video files can be larger or smaller depending on factors such as their length and quality.