Networks that led to the internet

X.25
Packet switching network standards were developed by the International Telecommunication Union in the form of X.25. X.25 formed the basis for the SERCnet network between British academic and research sites In 1974. The initial ITU Standard on X.25 was approved in March 1976. The British post office, and Tymnet collaborated to create the first international packet switched network. This network grew from Europe and the US to cover Hong Kong and Australia by 1981.
X.25 would be used for the first dial-in public access networks, like Compuserve and Tymnet. In 1979, CompuServe became the first service to offer e-mail capabilities and technical support to PC users. The company broke new ground again in 1980 as the first to offer real time chat with its CB Simulator.

UUCP
in 1979 two students at Duke university named Tom Truscott and Jim Ellis used Bourne shell scripts to transfer news and messages on a serial line. UUCP net also created gateways and links between FidoNet and dial up BSS hosts. UUCP networks spread quickly because of lower costs, Also because of the use of leased lines, x25 links or even ARPANET. the number of UUCP hosts had grown to 550 by 1983 and then nearly doubling by 1984