Appendix: Types of Microchips

[Kinds of chips]

Chips come in a variety of packages. The three most common are:

DIP's: Dual in-line packages are the traditional buglike chips that have anywhere from 8 to 40 legs, evenly divided in two rows.
PGA's: Pin-grid arrays are square chips in which the pins are arranged in concentric squares.
SIP's: Single in-line packages are chips that have just one row of legs in a straight line like a comb.

There are also single in-line memory modules (SIMMs), which consist of up to nine chips packaged as a single unit.