Stay informed with the
Recent Articles
Best of John Grochowski

# How virtual reels on a slot machine work

10 March 2009

It was a Monday morning — prime time for me when it comes to touring the casinos — and I was wandering down an aisle of three-reelers when I heard my name.

"You're John, right?"

I turned to acknowledge a woman, perhaps in her 50s, about 5-foot-2 with a touch of gray in her hair.

"I'm Ellie," she said. "I was at one of your seminars a couple of years ago, and there's something I've always wanted to ask you about the slots."

"You mentioned something about a virtual reel, and I wanted to know how that worked."

The symbols and blank spaces on the physical reel are mapped onto a virtual reel. Each stop on the virtual reel is assigned a number, and when that number comes up on a random number generator, the corresponding stop comes up.

"I think I get that. Could you give me an example?"

I took out my notebook and pen and started scribbling a simple example. Say I have a 20-stop physical reel with one 7, two triple bars, three double bars, four single bars and 10 blank spaces. And let's say I want it to behave as if it has 64 stops instead, with one of them being the 7, four of them being triple bars and so on.

I have the programmer tell the game's program that whenever No. 1 comes up, to have the 7 stop on the payline. Whenever No. 2 or No. 3 come up, have the first triple bar stop on the payline. Whenever No. 4 or No. 5 is generated, show the second triple bar. And I keep assigning numbers until I reach my target of 64.

"So the game is being played on the random number generator? The reels themselves are just doing what they're told by a computer?"

Right.

"Why?"

The virtual reel-random number generator combination make today's large slot jackpots possible. In the old days, when slot machines were mechanical, a game with three reels with 10 stops each hand only 1,000 possible combinations — 10 times 10 times 10. If there is just one top jackpot symbol on each reel, then there is only one way to line up three of 'em. That leaves a 1 in 1,000 chance of hitting the top jackpot.

You can't pay a very large jackpot if the big one is going to come up that often. One way to change that is to increase the size of the reels. If there are 20 stops per reel instead of 10, there are now 8,000 three-reel combinations — 20 times 20 times 20.

Manufacturers can only increase reel size so far before the reels become to big and cumbersome to fit in a machine. But with computerized slots, they have another option.

"The virtual reel?"

Right. If you can take that reel with 20 symbols or blanks and make it behave as if it has 64 stops instead, there are 262,144 possible combinations. With that, you can start paying some sizeable jackpots. If you want potential payoffs of really big bucks, you can make the virtual reel bigger without increasing the size of the physical reel. With 256 virtual symbols or spaces, there are nearly 17 million three-reel combinations — 16,777,216 to be exact. If only one symbol on each reel is the top jackpot award, the casino can start paying lifestyle-changing prizes.

With that, Ellie gave her thanks and started to walk away.

"Enough of the theory," she said with a laugh. "Now I need the practice."

** * ** * **

The virtual reel explanation above applies mainly to reel-spinning slot machines. Video slots present programmers with a different situation.

On the video slots, there are no physical reels. The reels are video images, so in that way all video slot reels are virtual, rather than real reels. But the need for the reel-spinners' map doesn't exist.

Why not? Because video reel strips take up no extra physical space, no matter how long they are. If a programmer needs a video reel to be 64 symbols long, he can just program a strip of 64 consecutive images — or 128 or 256 or whatever is needed to make the game work.

A physical reel with 64 symbols would be too large to fit easily in a slot machine cabinet. But a video reel with 64 symbols takes up no more physical space than one with 10.

Still, in either case, the real game is being played on the random number generator, which tells the reels — physical or on video — where to land.

Recent Articles
Best of John Grochowski
John Grochowski

John Grochowski is the best-selling author of The Craps Answer Book, The Slot Machine Answer Book and The Video Poker Answer Book. His weekly column is syndicated to newspapers and Web sites, and he contributes to many of the major magazines and newspapers in the gaming field, including Midwest Gaming and Travel, Slot Manager, Casino Journal, Strictly Slots and Casino Player.

Listen to John Grochowski's "Casino Answer Man" tips Tuesday through Friday at 5:18 p.m. on WLS-AM (890) in Chicago. Look for John Grochowski on Facebook and Twitter @GrochowskiJ.

#### Books by John Grochowski:

John Grochowski
John Grochowski is the best-selling author of The Craps Answer Book, The Slot Machine Answer Book and The Video Poker Answer Book. His weekly column is syndicated to newspapers and Web sites, and he contributes to many of the major magazines and newspapers in the gaming field, including Midwest Gaming and Travel, Slot Manager, Casino Journal, Strictly Slots and Casino Player.

Listen to John Grochowski's "Casino Answer Man" tips Tuesday through Friday at 5:18 p.m. on WLS-AM (890) in Chicago. Look for John Grochowski on Facebook and Twitter @GrochowskiJ.