Where Are We Going

1
Where Are We Going?

• CPSC 120
• Principles of Computer Science
• September 3, 2007

2
Course Themes

• Complexity and Structure
• Encoding and Decoding
• Hardware and Software
• Theory and Application
• Local and Remote

3
Quick Guide to the Future

• Basic Electricity Theory
• Switches, lights, and LEDs
• Logic of switches AND, OR, NOT
• Computing using logic Adders
• Arithmetic/logic units ALUs
• Central processing units CPUs
• Microprocessors Real devices
• A general view of a computer

4
When Hardware Meets Software A Robot Odyssey

• Programs are coded CPU instructions
• Programming in PBASIC to take control
• Meet the Basic Stamp II Microprocessor
• BOE Building a mobile robot
• Motors and sensor hardware control
• Robot programming Meet the real world
• Robot Exhibition line following, obstacles

5
Computing seen from very large to very small

• How about understanding computing by starting
  with the big picture?
• The largest tangible computing organization spans
  the entire world
• Lets start there and narrow down in search of
  the essentials to doing a computation
• We will see this approach presents some problems!

6
Earth at Night
7
Internet Connections
8
Computer Motherboard
9
A Computer Diagram
10
Microprocessor Central Processing Unit (CPU)
11
Very Large Scale Integration View of Chip
Interior
12
Individual Transistors
13
We are almost at the very bottom of the
complexity tower

• Question What do we know is fundamental to
  (all) computers?
• Answer Electricity
• So, to understand computers we should take the
  plunge and learn something about electricity.

14
Electricity and Computation(Short Version)

• Electricity is the flow of electrons
• Positively () charged areas attract electrons
  (-)
• Conductors (metal) allow electron flow
• Insulators (ceramic, air) prevent electron flow
• We can control electricity by switches
• Switches create a logic of on/off control
• Off/on, false/true, 0/1 encodes numbers also
• Arithmetic can be done using true/false logic
• We can code hardware control using 0/1s

15
Electricity and Circuits
A physical lamp circuit
The corresponding schematic
Single Pole-Double Throw Switch
An LED circuit using Power/GND symbols
16
Circuits All Around You

• How do I design a seatbelt safety circuit like
  the one in my car?
• How do I add a door ajar feature as well?
• How do I design a staircase lighting circuit like
  the one in my two story house?
• What about my three story house?
• What about my twelve story building?

17
What comes next?

• Actually handle some components in lab and make
  some simple circuits LEDs, etc
• Think hard about how to make some kind of useful
  circuits using simple switches
• Combine switches to create logic circuits
• Discover that logic and computation overlap in
  just the right way using base 2
• Make a circuit that computes something!