DIP

Dual in-line package (DIP or DIL), or dual in-line pin package (DIPP)is an electronic component package with a rectangular housing and two parallel rows of electrical connecting pins.
The package may be through-hole mounted to a printed circuit board (PCB) or inserted in a socket.
Eventually microprocessors and similar complex devices required more leads than could be put on a DIP package, leading to development of higher-density packages.
Furthermore, square and rectangular packages made it easier to route printed-circuit traces beneath the packages.
DIPs are commonly used for integrated circuits (ICs). Other devices in DIP packages include Resistor, Capacitors, DIP switches, LED segmented and Bargraph displays, and electromechanical relays.