Write a short note on ARPAnet.

ARPAnet (Advanced Research Projects Agency NETwork) is regarded as the first computer network. It was started by the U.S. Department of Defense in 1969 with the goal of connecting the computers at different universities and U.S. defense. It laid the foundations of today's internet. The users of this system began exchanging data and messages on it. They were also able to play long distance games and socialize with people who shared their interests leading to its rapid expansion. The original ARPANET was shut down in 1990.