Data Representation (Revised)

Data Representation (Revised)

1. Binary

   • Data needs to be converted into binary so that the computer can understand it. This is because computers work using machine code, and binary is a form of this. So any data from the outside world needs to be converted into binary numbers before the computer can process it.
   • To convert binary to denary, use a binary number line, going from left to right : 128 , 64 , 32 , 16 , 8 , 4 , 2 , 1
     • Then convert to hex!!

2. Hex

   • Hexadecimal is a base 16 system used to simplify how binary is represented. This means an 8-bit binary number can be written using only two different hex digits. It is much easier to write numbers as hex than to write them as binary numbers.
   • To convert denary to hex
     • 0 - 9 = 0 - 9
     • 10 - 15 = A - F
     • Eg : 11010100 in binary would be D4 in hex

3. 4 bits = 1 nybble

   • 2 nybbles in a byte (8 bits)
     • 1 kilobyte = 1024 bytes
       • 1 megabyte = 1024 kilobytes
         • And so on....

4. Unicode

   • Is an international encoding standard for use with different languages and scripts, by which each letter, digit, or symbol is assigned a unique numeric value that applies across different platforms and programs.
   • Advantages
     • Unicode is a 16-bit system which can support many more characters than ASCII
     • The first 128 characters are the same as the ASCII system making it compatable
     • There are 6400 characters set aside for the user or software
   • Disadvantages
     • Unicode files are very large because it takes 2 bytes to store each character.

5. ASCII

   • American Standard Code for Information Interchange
   • Advantages
     • Very small storage - 1 byte per character
   • Disadvantages
     • ◦ASCII is a 7-bit system which enables 128 binary patterns to be available to represent 128 different characters
     • Only has basic alphabets (lower and upper case) and common symbol

6. TRUTH TABLES ******** HELP!!!!!!!!!!!

7. Data Types

   • Integer
     • A whole number, positive or negative
   • Boolean
     • Data type with two values, usually true/false
   • Character
     • A single character - A/3/*
   • String
     • A sequence of characters, either as a literal constant or as some kind of variable. It allows its elements to be mutated and the length changed

8. How computers interpret instructions

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