1. How Computers Work Part 2 20 September 2006

2. About the Term Project  Your paper must take a position and be a proponent for it  Your presentation must cover both positions

3. Partnerships 1. Meet your partner 2. Communicate, communicate, communicate 3. Read your email 4. Agree to working rules  Meeting times  Work times  Communicating electronically 5. Before you hand in your summaries, you have 5 minutes  If you have problems, see me ASAP

4. Simplified Model of a Computer processor instructionsdata the information that it works on defines an algorithm retrieves the instruction directs data movement Control Unit Arithmetic Logic Unit MEMORY Performs the operations

5. Binary System  Everyone knows that computers store bits, right?  What does it mean? All data is stored as a series of zeroes and ones  Why? 1 0 =

6. Representing Numbers  Additive system ||||| ||||| Every item represents 1 Examples of additive systems?  Positional system Value = face * place 37 = 3*10 + 7*1 ||||

7. Positional System  Base = number of different values in a position Base 10 = 10 values: 0-9 Base 2 = 2 values: 0-1  Value of each position = power of base b 4 b 3 b 2 b 1 b 0 Binary: 2 4 2 3 2 2 2 1 2 0

8. Binary Positional System 1 0 = 0000 = 0010 = 8 4 2 1 = 0001 0100 = = 0011 0 1 2 3 4

9. Examples  2 4 2 3 2 2 2 1 2 0  16 8 4 2 1  Examples 1111 =  15 1000 = 88 01100100 =  100

10. Data Types  Computer doesn’t know what the bits represents or what format is being used  Computer assumes that the instructions know the format of the data  What are the types of data? Numbers, text, pictures, sound, instructions

11. Data Types  Numbers: integers and floating point numbers (scientific notation) Why do we need floating point numbers?  Text: Unicode, double byte Languages and symbols (Word insert symbol)  Pictures: pixels A very fine needlepoint How to represent color?  Sound: different formats  Instructions