Data Types

Character String

• usually hold text data
• text data consist of ASCII characters (characters whose code point <= 127)
• example: "hello world!" belongs to ASCII subset

Binary String

• usually hold binary data (pictures, voice, mixed mediaa)
• unit of length is OCTETS

• 2 types of varying-length binary string

  • VARBINARY value up to 32,672 bytes
  • BLOB (Binary Large Object) value up to 2GB - 1byte

ASCII

What is it lol

Stands for American Standard Code for Information Interchange - an early standardized encoding system for text. Encoding is converting characters in human language to binary sequences.

256 different ways to group eight 1s and 0s -> 256 ways to represent a character in ASCII.

For example

Character	ASCII	Byte
A	065	01000001
a	097	01100001
0	048	00110000
9	057	00111001
!	033	00100001

Problem

Not enough ways to store every symbol, ever.

Unicode

What is it lol?

• Unicode Standard is an international encoding standard for use with different languages and scripts where each letter, digit or symbol is assigned a unique numeric value (code point)
• allow representation of all languages: abc, language symbols, hiragana, katakana, emoji - in a unified way, up to 32 bits wide (~4 billion unique values)

For example

Character	Code Point
A	U+0041 or \u0041
a	U+0061 or \u0061
0	U+0030
9	U+0039
あ	U+3042
😁	U+1F601

U stand for "Unicode"

UTF is what leh

UTF stands for Unicode Transformation Format - 8 bits. It is an encoding system for Unicode (translate Unicode to binary string, string back to Unicode)

There are multiple encoding systems for Unicode:

• UTF-8 (8 bits - 1 byte) seen as more efficient as if a character can be represented in 1 byte, that is what it will use. Also, first 128 code points are exactly the same as ASCII
• UTF-16 (16 bits - 2 bytes)

UTF-8 saves space. In UTF-8, common characters like “C” take 8 bits, while rare characters like “💩” take 32 bits. Other characters take 16 or 24 bits. A blog post like this one takes about four times less space in UTF-8 than it would in UTF-32. So it loads four times faster. -Adam Hooper

Character	Code Point	Bytes Taken
A	U+0041	1
a	U+0061	1
0	U+0030	1
!	U+0021	1
😁	U+1F601	4

Javascript Engine uses UTF-16

> console.log("haha".length) 4 > console.log("😁".length) 2

Each character, 'h','a' uses 16 bits while fancy ones will use 32 bits. UTF-16 code units means using two code points to reference a character. Smallest binary representation of a character is 2 bytes, 16 bits.

CHARACTER	UTF-8 BINARY ENCODING	UTF-16 BINARY ENCODING
A	01000001	01000001 11011000 00001110 11011111
𠜎	11110000 10100000 10011100 10001110	01000001 11011000 00001110 11011111