Integrated circuits

"Integrated Circuits, also called ICs or informally, "microchips" or just "chips", are miniature electronic circuits built onto a single (very small) piece of silicon embedded in a package that allows it to be connected to a cicuit. They can fulfill many functions, ranging from simple logic gates and other simple devices such as counters and shift registers, to computer processors."
Advantages of ICs:
When ICs were introduced, they represented a revolutionary paradigm shift in the construction of electronic device. Rather than everything having to be made from basic components, certain standard modules could be plugged in in the form of a "microchip".
This reduces cost (a simple IC of the kind used in this Wikibook costs between 10p and £1), as opposed to the equivalent cost of potentially upwards of tens, or more likely, hundreds, of discrete components.
Also, as the devices are highly miniaturised, they take up less space, use less power, and operate faster with less noise, due to the components inside being very close together.
Modern ICs can fit up to 1,000,000 transitors onto a piece of silicon with an area of 1mm².
 Form of an IC:
All ICs have the same basic parts. At the heart of the IC is the die. This is the piece of silicon that the circuit is built on. It is generally smaller than 1mm on a side and is usually located in the geometric centre of the device.
The die is connected by fine wires (generally 20μm or thinner) to the pins. Pins are metal protrusions that are used to make contact with the outside circuitry. Pins usually take to form of the "legs" seen sticking out from the sides on most common microchips. Pins can also be vertical pins or tiny solder balls on the bottom surface of the IC.
The dies and the pins are set into the carrier. This is the body of the IC and is generally made of plastic or ceramic. To orientate the device, a notch, dot, or cut-off corner is usually included on the carrier.

ntegrated Circuits are usually called ICs or chips. They are complex circuits which have been etched onto tiny chips of semiconductor (silicon). The chip is packaged in a plastic holder with pins spaced on a 0.1" (2.54mm) grid which will fit the holes on stripboard and breadboards. Very fine wires inside the package link the chip to the pins.
IC pin numbers

Pin numbers:

The pins are numbered anti-clockwise around the IC (chip) starting near the notch or dot. The diagram shows the numbering for 8-pin and 14-pin ICs, but the principle is the same for all sizes.

IC holders (DIL sockets)

IC holder (DIL socket) ICs (chips) are easily damaged by heat when soldering and their short pins cannot be protected with a heat sink. Instead we use an IC holder, strictly called a DIL socket (DIL = Dual In-Line), which can be safely soldered onto the circuit board. The IC is pushed into the holder when all soldering is complete. IC holders are only needed when soldering so they are not used on breadboards.
Commercially produced circuit boards often have ICs soldered directly to the board without an IC holder, usually this is done by a machine which is able to work very quickly. Please don't attempt to do this yourself because you are likely to destroy the IC and it will be difficult to remove without damage by de-soldering.

Removing an IC from its holder:

If you need to remove an IC it can be gently prised out of the holder with a small flat-blade screwdriver. Carefully lever up each end by inserting the screwdriver blade between the IC and its holder and gently twisting the screwdriver. Take care to start lifting at both ends before you attempt to remove the IC, otherwise you will bend and possibly break the pins.