IC is an acronym for Integrated Circuit. It was developed about 50 years ago, and is used commonly for miniature electronic components using a large number of building blocks such as transistors. ICs have greatly facilitated the development of PCs, mobile phones and other electronic gadgets. They are used in every item of daily use now, such as credit cards, traffic lights and so on. Being extremely small, they occupy very little space, sometimes with dimensions of 5mm by 5mm and a thickness of 1mm or even less.
As the name indicates, an IC is an integrated composite mixture of items such as transistors, diodes, resistors, each serving a definite purpose. Whereas the transistor functions like a switch, resistors control the flow of electric current and the diode is for one-way passage of current.