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ICT Lesson, November 29 Notes

1. Data

Representation of Data
- Data are stored as 0 and 1 in a computer
  - Have electricity and no electricity
- Learn how to convert denary / hexadecimal into binary numbers :)
  - In binary numbers, every digit is a bit.
  - f3 math, go back to f3 if u don't know
  - Make sure to learn it as calculator can't help u every time :<
- Hexadecimal usage
  - IP Adresses (IPv6)
  - Color Codes (#FFFFFF)
- Types of representation of data
  - Text
  - Image
  - Audio
  - Video (Audio + Images)
- Unit in measuring data
  - 1bit = 1b
  - 8bit = 1 byte = 1B
  - 1024B = 1 Kilobyte = 1KB
  - 1024KB = 1 Megabyte = 1MB
  - 1024MB = 1 Gigabyte = 1GB
  - 1024GB = 1 Terabyte = 1TB
  - 1024TB = 1 Perabyte = 1PB
  - 1024PB = 1 Yetabyte = 1YB
  - 1024YB = 1 Zetabyte = 1ZB
  - And so how everything goes on...
  - Note: 1024 = 2^10
How is negative values stored in binary in PC?
- Sign and magnitude
  - The leftmost bit represent positive / negative.
  - 0 = positive and 1 = negative
    - e.g. 1001 is -1 and 0001 is 1
- Two's complement
  - 1. Specify the number of bits (e.g. 8)
  - e.g. -14
    - 00001110 = 14
    - Revert all the 0 and 1 -> 11110001
    - Two's complement of -14 -> 11110010 (add 1 at the end of the number)
    - so dumb and annoying