In the context of computers, the word slot has two meanings. The first is the narrow opening, as in the door of a vending machine. It can also be the area in between face-off circles in an offensive zone.
The other meaning is the area in front of the goaltender. This allows a clear view of the net. Wrist shots can be taken with better accuracy.
The use of the word “slot” is related to electronic gadget junkies. The term is used in reference to a variety of urban teenagers who are often addicted to their electronic devices.
Slots are also used in air traffic control at busy airports. They allow a single user to connect to a server on a dedicated connection.
In addition to allowing access to an object, slots can be used to receive signals. When called directly, slots follow normal C++ rules. But when the signal is connected to the slot, the slot will report a runtime error.
Slots are also commonly used in machinery. An example program connects the valueChanged() signal of QScrollBar to the display() slot.
When a slot is connected to a signal, the overhead is much lower than calling the receivers directly. However, it is still required to marshal parameters. Emitting a signal through slots is ten times slower than calling a receiver directly.
Although slots and signals are relatively simple, their overhead is very worth it. Especially when compared to the overhead of system calls.