A.I. System in Arcade Games

7.0 LAST WORDS

=======================================


Well in this tutorial we looked at Logic Gates 

and how they perform functions on binary numbers, 

Gates can be used to build up much better

and sophisticated functions such as loops and comparisons, 

used together these can easily perform multiplication 

and division and we can use these in everyday equipment, 

from washing machines and microwave ovens to motion sensitive 

cameras and pc's.



SHOUTS

=======================================



Starman_Jones - Thanks for everything over the years (

especially for my own room).



Vsus - I am never drinking Tsambuca with you again :P.



Delusive - Nice arse luv :P.



BSRF - Thanks to every-1 at BSRF for releasing this and for 

being a good laugh :).

6.0 BINARY ADDITION

=======================================



So we all know how to add decimal numbers (im presuming), its easy

 

 1 1 1

 + 1 + 2 + 3

 --- --- ---

 = 2 = 3 = 4



But how do we add in binary? Easy watch this



 0 0 1 1

 + 0 + 1 + 0 + 1

 --- --- --- ---

 = 0 = 1 = 1 = 10



Thats fine but with 1+1 we get a carry over that we have to 

deal with. So we add an extra space to handle the carry.



 0 0 1 1

 + 0 + 1 + 0 + 1

 --- --- --- ---

 = 00 = 01 = 01 = 10



Lets write a truth table to handle this data.



 A B | CO Q

 -------+--------

 0 0 | 0 0

 0 1 | 0 1

 1 0 | 0 1

 1 1 | 1 0



Notice the new column on the truth table for the carry out (CO).

We now notice that CO and Q and familiar, C0 is the same as an AND

gate and Q is the sa
		
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5.0 THE EXCLUSIVE GATES

=======================================

The final 2 gates remaining are the XOR (eXclusive OR) and

XNOR (eXclusive NOR) gates. Here they are.


5.1 THE XOR GATE

=======================================



The logic behind this gate is that if either A or B is equal

to 1 but not both then the output is equal to 1, here is its

truth table.



 A B | Q

 -------+------

 0 0 | 0

 0 1 | 1

 1 0 | 1

 1 1 | 0



The gate is constructed as follows.



 (A & ~B) | (~A & B)



 (0 & ~0) | (~0 & 0) = 0

 (0 & ~1) | (~0 & 1) = 1

 (1 & ~0) | (~1 & 0) = 1

 (1 & ~1) | (~1 & 1) = 0



5.2 THE XNOR GATE

=======================================



The XNOR gate is simply the opposite of the XOR gate, its truth

table looks like the followin
		
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4.0 NEGATED GATES

=======================================



There are 2 Negated Gates, these are the NOR and NAND gates. 

Basically these gates act like an OR and AND gate only there 

output is the opposite.





4.1 THE NAND GATE

=======================================



The truth table of a NAND gate is as follows



 A B | Q

 -------+------

 0 0 | 1

 0 1 | 1

 1 0 | 1

 1 1 | 0



Notice that it is the opposite of an AND gate.



 0 & 0 = 0, ~0 = 1



To wrap this up a bit better we use brackets ()



 ~(0 & 0) = 1

 ~(0 & 1) = 1

 ~(1 & 0) = 1

 ~(1 & 1) = 0



Now the result of the calcuation in the brackets is negated.




4.2 THE NOR GATE

=======================================



The truth table for the NOR gate is as follows

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3.0 THE LOGIC GATES

=======================================



Well binary is nice n easy n all but if thats all that a computer

understands then how does it go from that to a word processor or 

an entire operating system. Well we build up these complicated 

tasks using simple logic gates and boolean algebra, boolean 

algebra was created by George Boole in Ireland in the 1800's, 

wahey. The gates provide a way to make decisions and more 

complex tasks are built upon them. These gates accept input of 

Binary numbers and their output is based on the type of gate and 

what input was involved. There are three simple gates.



3.1 THE NOT GATE

=======================================



The simplest of all the gates is the NOT gate, it just takes 

a binary value of either 1 or 0 and gives back the oppossite. 

The NOT gate is symbolised by the operator '~'. Consider the
		
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2.1 A LITTLE CONVERSION

=======================================



So how do we convert from decimal to binary numbers? Sure you could

write out a table like above and check it to get the binary value

you want but what if your looking for a value for a number like

1275, good look writing a table up to 10011111011 or we could just

use the good old repeated division of 2 method. This works by

repeatedly dividing the decimal number by 2 and if its an even number

record a 0, if its an odd record a 1. Say for example we wanted to

convert 57 to binary:



2/57 remainder = 1

= 28



2/28 remainder = 0

= 14



2/14 remainder = 0

= 7



 2/7 remainder = 1

= 3



 2/3 remainder = 1

= 1



 2/1 remainder = 1

= 0



Now if we put those remainders alongside eachother starting from the

bottom up w
		
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A QUICK LOOK AT BINARY

=======================================



Basically binary is very simple, we as people are used to counting

 in decimal, 1,2,3, etc..., this is known as base 10 as their are 

10 numbers in decimal 0,1,2,3,4,5,6,7,8,9 and no 10 is not one of 

them, to get ten we put 1 and 0 together when we move past 9, 

we do this in order to count higher, obviously, and once we get 

passed 9 we go back to 0 move over one space and put on a 1.



 0

 1

 2

 3

 4

 5

 6

 7

 8

 9 <- Reached the maximum of our numbers in decimal

 10 <- So we move over one place and put on a 1 and start again

 11

 12

 13

 14

 15

 16

 17

 18

 19 <- Again we reach the maximum so we move over one place and 
 add a 1

 20

 21

 ..

 ..

 90 <- And so on 
		
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