4.5.3.1 Bits and bytes

A bit is a fundamental unit of information that can either store a 0 or a 1. Computers cannot just deal with one bit at a time, as they are too small. Computers usually deal with 8 bits at a time.

Unit Bits Number of Values
bit 1 \(2^1 = 1\)
nibble 4 \(2^4 = 16\)
byte 8 \(2^8 = 256\)
word 16 \(2^{16} = 65536\)
dword (doubleword) 32 \(2^{32} = 4294967296\)
qword (quadword) 64 \(2^{64} = 9223372036854775807\)

4.5.3.2 Units

Quantities of bytes can be described using binary or decimal prefixes.

Decimal Name Bytes Binary Name Bytes
Kilobyte \(10^3\) Kibibyte \(2^{10}\)
Megabyte \(10^6\) Mebibyte \(2^{20}\)
Gigabyte \(10^9\) Gibibyte \(2^{30}\)
Terabyte \(10^{12}\) Tebibyte \(2^{40}\)