Stands for "Transmission Control Protocol/Internet Protocol." These two protocols were developed in the early days of the Internet by the U.S. military. The purpose was to allow computers to communicate over long distance networks. The TCP part has to do with the verifying delivery of the packets. The IP part refers to the moving of data packets between nodes. TCP/IP has since then become the foundation of the Internet. Therefore, TCP/IP software is built into all major operating systems, such as Unix, Windows, and the Mac OS.