How Computers Work

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 • Meet your partner • Communicate, communicate, communicate • Read your email • Agree to working rules • Meeting times • Work times • Communicating electronically • Before you hand in your summaries, you have 5 minutes • If you have problems, see me ASAP

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

5. 1 = 0 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?

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 • b4 b3 b2 b1 b0 • Binary: 24 23 22 21 20

8. 8 4 2 1 0 1 = 0 0 0 0 = 1 0 = 0 0 0 1 2 = 0 0 1 0 3 = 0 0 1 1 4 = 0 1 0 0 Binary Positional System

9. Examples • 24 23 22 21 20 • 16 8 4 2 1 • Examples • 1111 = • 15 • 1000 = • 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