Bits and bytes

A bit is a single true/false value and is the smallest value computers can manipulate.

A byte is 8 bits, and every size stored on a computer is in bytes.

A word is the word-length of the processor, usually 32 bits or 64 bits.

Units

Bytes can be given in two different kinds of units:

• Decimal prefixes
• Binary prefixes

Decimal prefixes

The decimal prefixes are in powers of ten, with the usual scientific units:

• A kilobyte (k) is $ 10^3 $ bytes.
• A megabyte (M) is $ 10^6 $ bytes.
• A gigabyte (G) is $ 10^9 $ bytes.
• A terabyte (T) is $ 10^12 $ bytes.

Binary prefixes

The binary prefixes are in powers of two, and are preferred in programming due to them being faster to work with.

• A kibibyte (Ki) is $ 2^10 $ bytes.
• A mebibyte (Mi) is $ 2^20 $ bytes.
• A gibibyte (Gi) is $ 2^30 $ bytes.
• A tebibyte (Ti) is $ 2^40 $ bytes.