At the smallest scale in the computer, information is stored as bits và bytes. In this section, we"ll learn how bits và bytes encode information.

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## Bit

a "bit" is atomic: the smallest unit of storageA bit stores just a 0 or 1"In the computer it"s all 0"s & 1"s" ... BitsAnything with two separate states can store 1 bitIn a chip: electric charge = 0/1In a hard drive: spots of North/South magnetism = 0/1A bit is too small to be much useGroup 8 bits together khổng lồ make 1 byteEverything in a computer is 0"s and 1"s. The bit stores just a 0 or 1: it"s the smallest building block of storage.

## Byte

One byte = collection of 8 bitse.g. 0 1 0 1 1 0 1 0One byte can store one character, e.g. "A" or "x" or "\$"

## How Many Patterns With N Bits? (demo)

How many different patterns can be made with 1, 2, or 3 bits?Number of bits Different Patterns
1 0 1
2 00 01 10 11
3 000 001 010 011 100 101 110 111
3 bits vs. 2 bitsConsider just the leftmost bitIt can only be 0 or 1Leftmost bit is 0, then append 2-bit patternsLeftmost bit is 1, then append 2-bit patterns again3-bits has twice as many patterns as 2-bitsNumber of bits Different Patterns
1 0 1
2 00 01 10 11
3 000 001 010 011 100 101 110 111
In general: add 1 bit, double the number of patterns1 bit - 2 patterns2 bits - 4 3 bits - 84 bits - 165 bits - 326 bits - 647 bits - 1288 bits - 256 - one byteMathematically: n bits yields 2n patterns (2 to lớn the nth power)

## One Byte - 256 Patterns (demo)

1 byte is group of 8 bits8 bits can make 256 different patternsHow khổng lồ use the 256 patterns?How to store a number in a byte?Start with 0, go up, one pattern per number, until run out of patterns0, 1, 2, 3, 4, 5, ... 254, 255One byte can hold a number between 0 & 255i.e. With 256 different patterns, we can store a number in the range 0..255 Really good for storing characters/letters.

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## Bytes

"Byte" - unit of information storageA document, an image, a movie .. How many bytes?1 byte is enough to hold about 1 typed character, e.g. "b" or "X" or "\$"All storage is measured in bytes, despite being very different hardwareKilobyte, KB, about 1 thousand bytesMegabyte, MB, about 1 million bytesGigabyte, GB, about 1 billion bytesTerabyte, TB, about 1 trillion bytes (rare)

## Bytes & Characters - ASCII Code

ASCII is an encoding representing each typed character by a numberEach number is stored in one byte (so the number is in 0..255)A is 65B is 66a is 96space is 32"Unicode" is an encoding for mandarin, greek, arabic, etc. Languages, typically 2-bytes per "character"
 32 space33 !34 "35 #36 \$37 %38 &39 "40 (41 )42 *43 +44 ,45 -46 .47 /48 049 150 251 352 453 554 655 756 857 958 :59 ;60 63 ?64 65 A66 B67 C68 D69 E70 F71 G72 H73 I74 J75 K76 L77 M78 N79 O80 P81 Q82 R83 S84 T85 U86 V87 W88 X89 Y90 Z91 <92 93 >94 ^95 _96 ` 97 a98 b99 c100 d101 e102 f103 g104 h105 i106 j107 k108 l109 m110 n111 o112 p113 q114 r115 s116 t117 u118 v119 w120 x121 y122 z123 125 126 ~

## Typing, Bytes, và You

Each letter is stored in a byte, as below100 typed letters takes up 100 bytesWhen you send, say, a text message, the numbers are sentText is quite compact, using few bytes, compared to images etc.