Scoblete calls it the "god in the machine" in Break the
One-Armed Bandits. Players know that it determines the symbols that
land on the payline on a slot machine and the cards they're dealt
on a video poker machine. It's the Random Number Generator or RNG
in the machine. Let's take a close look at what the RNG is and how
slot and video poker machines use it.
The RNG can either be a separate computer chip on
one of the boards in the machine or it can just be part of the program
that runs the slot machine. Either way, the RNG is nothing more
than a series of mathematical steps performed on one number to generate
another number. Those steps can be quite involved, so I won't go
into any examples here. I'll just let this sample output from an
RNG suffice. Suppose we start with the number 7 and feed it into
our RNG. The RNG returns a 2. We feed the RNG the 2 and we get back
an 8. We feed in the 8 and get a 9. We continue doing this and we
end up with this series of numbers: 7, 2, 8, 9, 3, 6, 5, 1, 4, 7,
2, 8, etc. Once the RNG returns a 7, the pattern repeats.
Now, we have to take a quick digression and clean
up some of our terminology. First, what is a random number? Is 13
a random number? How about 2,145,298?
Randomness is not a property of a number. Numbers
can be odd, even, integer, non-integer, etc., but random is not
a property of a single number. A sequence of numbers, however, can
be random. Random in this context means that knowing one number
in the sequence does not help you predict what the next number in
the sequence will be.
You may recall from the RNG example I used before
that we used the last number output from the RNG to calculate the
next number. If we knew the formula used in the RNG and the last
number produced, we'd be able to calculate the next number. That
certainly doesn't fit the definition of random I just gave.
The RNG in a machine is more correctly called a
Psuedo-Random Number Generator. The number sequence from a Psuedo-RNG
satisfies many of the tests for randomness that we can perform,
but the sequence is not truly random because given the current number,
we can calculate the next number in the sequence.
So, we have this RNG function in our machine. In
the early days of computer-controlled slot machines, the machines
worked quite differently from today's machines. The computers were
not as powerful as those used today, so the machine would figure
out the outcome of the next spin as soon as the current spin was
finished. And the machine would sit there waiting for someone to
play it so it could reveal the outcome that it had already determined.
Sitting with an outcome locked in made it easy for
RNG cheats. They were able to figure out where the RNG was in the
sequence, so they would know what the outcome of any spin would
be. Then they could bet full coin on the winning spins and one coin
on the losers.
The computers in today's machines are much more
powerful and the RNG is constantly running, generating new outcomes.
The outcome you see is the number produced by the RNG at the split
second you push the spin button or pull the handle. How quickly
does the RNG run? It depends on the machine. An RNG can generate
from hundreds to thousands of outcomes each second.
Now, what does the machine do with the output from
the RNG? Let's look at slot machines first. The machine has to somehow
take a number and map it into the symbols to display on the payline.
Here's one way a machine can do this.
Let's say our machine has five reels with 100 symbols
on each reel. This is either a Big (BIG) Bertha or a video machine.
We'll make our solution real easy and get a separate number for
each reel. The player hits the spin button and we check the RNG
for the last number it generated. The number might be 2,347,174,
but we only need numbers from 1 to 100, so we ignore everything
but the last two digits and get 74. The first reel will stop on
stop 74. We repeat the same process to get the stops for the remaining
If this was a reel-spinning slot machine with only
22 physical stops per reel, there would be an additional step in
the process. Let's redo the example for the first reel. The RNG
tells us to stop on stop 74, but stop 74 doesn't exist. The output
from the RNG tells us virtual stops, not physical stops. The program
has to check a table in the program that says the physical stop
that each virtual stop represents. This is the technique used to
make the jackpot symbol appear much less frequently than the cherry
symbol. There may be two cherry symbols and two jackpot symbols
on a reel, but the jackpot symbol may appear only twice in the virtual
reel table and the cherry symbol may appear 20 times.
machines use the output from the RNG differently from a slot