CCCS #5 The ALU

This video is about how computers calculate - using the ALU - Arithmetic Logic Unit. It shows the way one is constructed and how it works.  This video is useful for A level Computer Science - you need to understand the principles of logic gates - half adders and full adders for that. 

The logic gates are also useful to know for GCSE of course. 

Now try Video #6

1) What is the role of the ALU? 

2) What is adding one to a number known as?

3) True and False are represented in binary how?

4) Draw a truth table for and XOR gate. 

5) Which logic gates make up a Half Adder? 

6) What is the AND gate used for? 

7) What is a Full Adder made up of? 

8) What is an overflow error?

9) What level in the original PAC-MAN caused an overflow - why?

10) Which Intel ALU  is mentioned at least twice in this video?  Why was it significant? 

11) How many bits could it add? 

12) What is the role of a flag bit in an ALU? 

13) Describe an example of how the negative flag can be used.