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Base 2 or Binary
 Why do you suppose you know base 10?
 We use base 2, or binary in computing.
 Probably because it is easy to tell if there is a positive charge or not.
 Or if a switch is on or off.
 As we will see, this is not the only way we could do it.
 But it is the way we do it.
 Comparison with base 10
 In base 10 there are 10 digits, {0,1,2,3,4,5,6,7,8,9}
 In base 2 there are 2 digits {0,1}
 In base 10, the radix is 10
 In base 2, the radix is 2
 In base 10 a number is : $d_n10^n + d_{n1}10^{n1} + ... + d_110+d_0$, where $d_i \in \{0,1,2,3,4,5,6,7,8,9\}$
 In base 2 a number is : $d_n2^n + d_{n1}2^{n1} + ... + d_12+d_0$, where $d_i \in \{0,1\}$
 We subscript binary numbers with a 2, to indicate binary.
 $10110_2$ is a binary number
 10110 is a decimal number
 In general we do not subscript base 10 numbers.
 But if we want $10110_{10}$ is what we would write.
 Some Terms
 A single binary digit is called a bit.
 A collection of 8 bits is called a byte.
 The first bit is the most significant bit (MSB).
 The last bit is the least significant bit (LSB).
 The term word is hardware dependent.
 It means the "size of data" in a computer.
 Some other terms, less frequently used
 Multiple words, bits and bytes
 Word:
 A half word is half of a word
 A double word is two words
 A quad word is four words.
 We know these terms from programming (double, quad, ...)
 Bits and bytes use the metric prefixes

value  Metric 
$10^3$  kilo (k) 
$10^6$  mega (M) 
$10^9$  giga (G) 
$10^{12}$  tera (T) 
$10^{15}$  peta (P) 
$10^{18}$  exa (E) 
$10^{21}$  zetta (Z) 
$10^{24}$  yotta (Y) 
$10^{27}$  ronna (R) 
$10^{30}$  quetta (Q) 
 In metric we use the term bit/byte so
 1kb (b is for bit) is 1,000 bits.
 1kB (B is for byte) is 1,000 bytes or 8,000 bits.
 1 Yb is 1,000,000,000,000,000,000,000,000 bits, and that is a lotta bits!
 A second system by the IEC defines prefixes in powers of 2.
value  Metric 
$2^{10} = 1024^1$  kibi (k) 
$2^{20} = 1024^2$  mibi (M) 
$2^{30} = 1024^3$  gibi (G) 
$2^{40} = 1024^4$  tebi (T) 
$2^{50} = 1024^5$  pebi (P) 
$2^{60} = 1024^6$  exbi (E) 
$2^{70} = 1024^7$  zebi (Z) 
$2^{80} = 1024^8$  yobi (Y) 
 So in this system
 5 kibibytes (KiB) = 5 x 2^10 bytes.
 I am fairly certain that this system was introduced due to a lawsuit where advertisers misused the term megabyte
 And I really don't care
 But I think you should know up to yotta.
 Because look here.
 What types of devices are measured in bits, bytes, and the other units?