1. Computer Systems – Logic Gates Introduce the basic logic gates Introduce truth tables Introduce Boolean algebra (dont panic!) Examples of combining gates

2. AND gate A B A B All inputs have to be true ( i.e 1) for the output of the gate to be high, in all other cases the output is false.

3. OR gate A B A B If any of the inputs are true then the output is true

4. A _ A _ A NOT gate The output of a NOT gate is the opposite of the input, in other words the gate inverts the input, so is often called an inverter.

5. NAND gate The opposite of an AND gate when any of the inputs are false the output is true Equivalent to A B A B

6. A B A B Equivalent to The opposite of the OR gate, the gate is only true when none of the inputs are true. NOR gate

7. A B Exclusive OR (XOR) In a 2-input the gate is only true when the inputs are different.

8. Boolean Algebra

9. Examples

10. Summary Introduced – Basic logic gates – Combined gates – Boolean Logic – Truth Tables

11. Sources for further reading Chalk et al (2004) pages 26-27. Dick (2002) pages 98-100 Burrel (2004) Chapter 3 - pages 43 -47 Tanenbaum (2005) pages 135-140