Until the late 1960s, every computer was a self-contained data world. You could run your programs on the machine in your data center, but not transfer the data elsewhere. Later on, remote data transmission made it possible to communicate with a computer via a telephone connection. If a computer and a person can communicate in this way (through a remote input/output device), why are computers not able to communicate with each other? This is where the idea of networking was born. In the early 1980s, the ARPA-Net started a network with a few computers. In 1985 there were 2000 computers, in 1990 over 300,000, in 2000 over 100 million and in 2013 around 1 billion.
