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# Casino Random Number Generators

28 July 2000

Dear John,

Do you think that there are some random number generators that are more customer friendly and some that are more generous to the casinos?

Thanks,
Rose Mary

Dear Rose Mary:

No. There aren't any random number generators that are better for the players and others that are better for the casinos.

There are, however, machines that are better for the players. Compare two Double Diamond machines. One has an 85% payback and the other 95%. It will seem like the RNG in the 95% machine is better for the players, but the truth is that the RNGs are the same in both machines. The difference is that the virtual reels in the higher payback machine probably have more paying symbols on them.

The program running the slot machine takes the number generated by the RNG and uses it to determine where to stop each of the machine's reels. Converting the number to a virtual stop is just a mathematical operation, and different methods may be used in different machines. The actual mechanics of the conversion are not important.

On the high payback machine, let's say virtual stops 20-25 map to one of the single bar symbols on the reel. On the low payback machine, only stops 20-23 map to the single bar symbol and stops 24 and 25 map to a blank symbol. The RNG operates such that each virtual stop on each reel is equally likely to be chosen, but it will appear that the RNG on the high payback machine is better for the players because the single bar symbol appears more frequently than on the low payback machine. In reality, the reason more single bar symbols land on the payline on the high payback machine is because there are more single bar symbols on the virtual reels on that machine.

In computer programming, this technique is called "indirection." Instead of accessing some resource directly, you go through an intermediate step. You can do all sorts of wonderful things in that intermediate step. The program in the slot machine uses indirection to map the 22 physical stops on a reel to 32, 64, 72 or more virtual stops on the virtual reel, which exists only in the programming in the machine.

Best of luck in and out of the casinos!
John

Send your slot and video poker questions to John Robison, Slot Expert, at slotexpert@home.com.

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John Robison

John Robison is an expert on slot machines and how to play them. John is a slot and video poker columnist and has written for many of gaming’s leading publications. He holds a master's degree in computer science from the prestigious Stevens Institute of Technology.

You may hear John give his slot and video poker tips live on The Good Times Show, hosted by Rudi Schiffer and Mike Schiffer, which is broadcast from Memphis on KXIQ 1180AM Friday afternoon from from 2PM to 5PM Central Time. John is on the show from 4:30 to 5. You can listen to archives of the show on the web anytime.

#### Books by John Robison:

The Slot Expert's Guide to Playing Slots
John Robison
John Robison is an expert on slot machines and how to play them. John is a slot and video poker columnist and has written for many of gaming’s leading publications. He holds a master's degree in computer science from the prestigious Stevens Institute of Technology.

You may hear John give his slot and video poker tips live on The Good Times Show, hosted by Rudi Schiffer and Mike Schiffer, which is broadcast from Memphis on KXIQ 1180AM Friday afternoon from from 2PM to 5PM Central Time. John is on the show from 4:30 to 5. You can listen to archives of the show on the web anytime.

#### Books by John Robison:

The Slot Expert's Guide to Playing Slots