Bits, Bytes and Characters

Computer Science 101, what is bit, bytes, character and unicode

Transcript

1. Bits, Bytes and Characters Shaikhul Islam Chowdhury dev.to/shaikhul github.com/shaikhul
2. Bit • Smallest unit of storage • Bit is 0 or 1 • 8 bits - 1 Byte
3. Byte • Group of 8 bit • 1 bit pattern - 0, 1 - 2 entry • 2 bit pattern - 00, 01, 10, 11 - 4 entry • n bit - 2^n entry possible • 1 Byte ◦ 8 bit - 2^8 - 255 entry ◦ Can hold 0 - 255 numbers
4. Bytes • How many bytes? • All storage are measured in Bytes • Bigger units ◦ KB (1000 B), ◦ MB (1000 KB), ◦ GB (1000 MB), ◦ TB (1000 GB) etc
5. Character and Unicode • Characters are represented as code point - range 0 - 0x10FFFF ( 1 million) Character Unicode Code Point Glyph Latin small letter a 0x61 a Black chess knight 0x265E ♞ Euro currency 0x20AC €
6. Character and Unicode (Code Point) Python In [22]: chr(0x0041) Out[22]: 'A' In [23]: chr(0x00df) Out[23]: 'ß' In [24]: chr(0x6771) Out[24]: '東' In [25]: chr(0x10400) Out[25]: '' Java jshell> new String(Character.toChars(0x0041)) $13 ==> "A" jshell> new String(Character.toChars(0x00df)) $14 ==> "ß" jshell> new String(Character.toChars(0x6771)) $15 ==> "東" jshell> new String(Character.toChars(0x10400)) $16 ==> ""
7. (Character) Encoding • Unicode string is a sequence of code points (limit 0 - 0x10FFFF) • character encoding - translate sequence of code points into Bytes to store into memory ◦ ASCII: 7 bit (0 - 127), english letters ◦ UTF-8: most common, default in python ◦ UTF-16 etc
8. (Character) Encoding - String to Bytes Python In [40]: c = chr(0x20ac) In [41]: c Out[41]: '€' In [42]: c.encode('utf-8') Out[42]: b'\xe2\x82\xac' Java jshell> String str = new String(Character.toChars(0x20ac)) str ==> "€" jshell> import java.nio.charset.* jshell> byte bytes[] = str.getBytes(StandardCharsets.UTF_8) bytes ==> byte[3] { -30, -126, -84 } jshell> for (byte b: bytes) { System.out.printf("%x ", b); } e2 82 ac
9. References • Stanford CS 101 on Bits and Bytes • Unicode HOWTO — Python 3.9.1 documentation • Unicode (The Java™ Tutorials > Internationalization > Working with Text)
10. Thank You