Slot is a term used in a variety of ways, most often referring to a narrow aperture or groove. Traditionally, slots are used for airflow in aircraft wings and tail surfaces, but they can also be found in auxiliary structures such as ailerons and flaps. They are designed to reduce drag by allowing air to flow over a larger surface area than it would otherwise.
The term slot also refers to a container that holds dynamic items on the Web page. A slot can contain a single item (passive slot) or several items (active slots). A scenario specifies the content to be placed in the slot, and a renderer specifies how the contents of the slot should be presented to the user.
In a mechanical slot machine, a player inserts cash or, in ticket-in, ticket-out machines, a paper ticket with a barcode, which activates reels that spin and stop to rearrange symbols. Winning combinations earn credits based on a pay table. The symbols vary, but classics include fruits, bells, and stylized lucky sevens. Most slot games have a theme, and the symbols and bonus features are aligned with that theme.
In C++, signals and slots are a way to use function pointers without the performance penalty of a non-virtual call. Emitting a signal connected to multiple slots is roughly ten times slower than calling the receivers directly, due to the overhead of finding the connection object and safely iterating over all connections, as well as marshalling arguments in a generic fashion.