Tomlinson worked for Bolt Beranek and Newman (BBN), the company hired by the United States Defense Department in 1968 to build ARPANET, the precursor to the Internet. In 1971 he was tinkering around with an electronic message program called SNDMSG, which he had written to allow programmers and researchers who were working on Digital PDP-10s—one of the early ARPANET computers—to leave messages for each other.
But this was not e-mail, exactly. Like a number of then existing electronic message programs, the oldest dating from the early 1960s, SNDMSG only worked locally; it was designed to allow the exchange of messages between users who shared the same machine. Such users could create a text file and deliver it to a designated "mail box."
"A mailbox was simply a file with a particular name," Tomlinson later wrote. "Its only special property was . . . [users] could write more material onto the end of the mailbox, but they couldn't read or overwrite what was already there."
When Tomlinson sat down to play around with SNDMSG, he had been working on an experimental file transfer protocol called CYPNET, for transferring files among linked computers at remote sites within ARPANET. (At the time, the ARPANET consisted of 15 nodes, located at places like UCLA in California, the University of Utah in Salt Lake City, and at BBN in Cambridge, Massachusetts.) "The idea occurred to me that CYPNET could append material to a mailbox file as readily as SNDMSG could," explained Tomlinson.
The way CYPNET was originally written, it sent and received files, but had no provision for appending to a file. So he set out to adapt CYPNET to use SNDMSG to deliver messages to mailboxes on remote machines, through the ARPANET.
"Adding the missing piece was a no-brainer," according to Tomlinson. "Just a minor addition to the protocol." What Tomlinson did next, if he had fully grasped its significance, might have earned him a place alongside the giants of communication history.
First, he chose the @ symbol to distinguish between messages addressed to mailboxes in the local machine and messages that were headed out onto the network. "The @ sign seemed to make sense," he recalled. "I used the @ sign to indicate that the user was 'at' some other host rather than being local."
Then he sent himself an e-mail message. BBN had two PDP-10 computers wired together through the ARPANET. "The first message was sent between two machines that were literally side-by-side. The only physical connection they had, however, was through the ARPANET," according to Tomlinson.
The message flew out via the network between two machines in the same room in Cambridge; and the message was QWERTYIOP. Or something like that.
..taken from http://www.pretext.com
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