If we just stop to think for a second, we'll realize that computers depend on programs to function. and what is a program? a pre-determined code. Now, how does one remain random when the programmer has already told us how to go about it? Computers use what is called a 'seed' or an initial value, a random number that is the starting point for the series. This random number could be the time or the number of keystrokes till that point of determination. They could even be based on things like the degeneration of atoms or statistical data gathered from internet sources. Point is, the initial values cannot be predicted. But once you know the initial state of the code, you can pretty much know every number that comes after it because it follows a particular set of instructions to generate randomness.
So much for a true slot-machine experience. The machine may look like it's rolling manually and stopping because of physical forces. But the truth is that the interface is controlled by a program that generates 'random' sets of results. That's why the Gaming Commission in Nevada is so strict. If no one checked the algorithms, we might never be able to beat casinos. Same with card games online.
And what about apple's celebrated shuffle function? There have been conspiracy theories that say that record labels can sneakily get apple to make the algorithm function in such a way that the shuffle plays their songs more than others. This is probably untrue but not altogether impossible.
