The earlier slot machine lacked the presence of a button which was replaced by a lever. Now days, instead of liver an electronic button is being employed which makes it much easier for the player to play the slot machine. Still there are few slot machines which have both a lever and button installed in them.

The important property of a slot machine is the presence of a cash detector whose main job is to detect whether the cash or the coin inserted by the player into the machine is real or not. The slot machine has a big screen which is used to display the combination that a person gets on pressing the button. If the combination is correct than the person wins and if not than he loses. As the technology is improving day by day, we are seeing a number of variations which are being incorporated in numerous slot machines. A computer is also installed in a slot machine. Almost 75% of the casinos income is obtained from slot machines.

The first ever gambling machine was invented by two people known as Pitt and Sittman who were originally from Brooklyn in New York, United States of America. This machine was an ancestor of the modern day slot machine. The machine initially consisted of five drums which were made to hold 50 playing card faces. It was typically a poker based machine. The popularity of this machine increased at a very fast rate and almost every bar owner in the town had this machine installed in his bar. 

The machine operated whenever a player would put a coin in the coin slot and either pulled a lever or hokifreebet pressed a button. After doing this, the 5 drums which this machine contained would start spinning along with the cards it was holding and thus would ultimately show us the combination which we would get. Earlier there was an indirect prize for a stated combination such as two kings would result in a free glass of scotch or all cards of same color would result in a free pack of cigars etc.