Computer coding
ascii
Only machine-executable binary code, a byte (byte) is eight bits (bit) 256 kinds of characters can be expressed
in English corresponding to the 128-bit ascii code
unicode
Placed in a multilingual environment is not enough to use, we found a workaround for the Complete Works: unicodeThis symbol set defines the binary code symbols, but does not specify how to store.
For instance 严binary code 100111000100101, aShi 01000001.
This variable length, one computer can not divide a specific character, but if unified into a fixed byte length will cause great waste of memory.
utf-8
utf-8 is unicode one implementation, the characteristics of variable length.
utf-8 rules:
- 使用1-4个字节表达字符
- 如果第一个字节的开头为0，那么这个为单字节字符，可表达128位字符与ascii码一样
- 如果字符需要用n(n > 1)个字节表示, 那么第一个字节的开头n位为1，n+1位为0，第2个至第n个字节的前两位一致设为10
utf-8 table
Change
| Byte count | utf-8 | range | Decimal | Hex | unicode |
|---|---|---|---|---|---|
| 1 | 0xxxxxxx | 00000000 ~ 01111111 | 0 ~ 127 | 0 ~ 7F | |
| 2 | 110xxxxx 10xxxxxx | 11000001 10000000 ~ 11011111 10111111 | 128 ~ 2047 | 80 ~ 7FF | |
| 3 | 1110xxxx 10xxxxxx 10xxxxxx | 111000000 10100000 10000000 ~ 11101111 10111111 10111111 | 2048 ~ 65535 | 800 ~ FFFF | |
| 4 | 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx | 11110000 10010000 10000000 10000000 ~ 11110111 10111111 10111111 10111111 | 65536 ~ 2097151 | 10000 ~ 1FFFFF |
Text class resource utf-8
- html
- css
- javascript
Picture categories Resources
base64
sixth power of 2 64
Principle:
. 8 3 = 6 . 4
- Taking a set of three characters, reproduced as in the form of 6 * 4
- Conversion table generation control base64
Thoughts: advantages and disadvantages?
Disadvantages: content increases, which can not be cached into html
advantages: You can print pass, picture resources in a Web page does not need to load additional http request
video Audio resources
Reference links
Ruan Yifeng character encoding notes
Original: Large column distal commonly used encoding format