Lecture 3 - Digital Representation

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ASCII

- American Standard Code for Information Interchange (ASCII) is a 7-bit characters code, with value from 0-127.
               
         




- Representing Sound: Sounds should be converted to binary for computer to process.
- Representing Image: When you have image, it is broken up into individual pixels.
- Representing Number: A number in a computer system is represented by a string of bits called binary numbers.

Number System
- Computers use binary number system in two states - on and off.

- In computing, we also use:
    1. Decimal (Base 10) Number System
      - Has ten symbols: 0,1,2,3,4,5,6,7,8 and 9, called digits.
        eg;,  735 = 700 + 30 + 5 = 7*10^2 + 3*10^1 + 5*10^0
      
    2. Binary (Base 2) Number System
      - Has two symbols: 0 and 1, called bits.
        eg;.  10110B = 10000B + 0000B + 100B + 10B + 0B = 1*2^4 + 0*2^4 + 1*2^2 + 1*2^1 + 0*2^0

    3. Octal (Base 8) Number System
      - It has 8 symbols: 0 to 7 (positional notation).
        eg;, 2370 = 2000 + 300 + 70 = 2*8^2 + 3*8^1 + 7*8^0

    4. Hexadecimal (Base 16) Number System
      - It has 16 symbols: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E and F (hex digits).
        eg;, A3EH = A00H + 30H + EH = 10*16^2 + 3*16^1 + 14*16^0






 

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