Encyclopedia of Computer Science and Technology

embedded system 177Instead, companies such as Microsoft and Google competeto offer full-featured e-mail programs that include grouporientedfeatures such as task lists and scheduling (see alsopersonal information manager).Transmission of an e-mail message depends on widely used protocolssuch as SMTP, which controls message format and processing,and POP3, which handles interaction between mail servers andclient programs. As long as the formats are properly followed, userscan employ a wide variety of mail programs (agents), and serviceproviders can use a variety of mail server programs.system, open the file, and look for messages. In 1971, however,the ARPANET (ancestor of the Internet—see internet)was used by researchers at Bolt Beranek and Newman(BBN) to send messages from a user at one computer to auser at another. The availability of e-mail helped fuel thegrowth of the ARPANET through the 1970s and beyond.As e-mail use increased and new features were developed,the question of a standardized protocol for messagesbecame more important. By the mid-1980s, the world ofe-mail was rather fragmented, much like the situation inthe early history of the telephone, where users often had tochoose between two or more incompatible systems. Apranet(or Internet) users used SMTP (Simple Mail Transport Protocol)while a competing standard (OSI MHS, or MessageHandling System) also had its supporters. Meanwhile, thedevelopment of consumer-oriented online services such asCompuServe and America Online threatened a further balkanizationof e-mail access, though systems called gatewayswere developed to transport messages from one system toanother.By the mid-1990s, however, the nearly universal adoptionof the Internet and its TCP/IP protocol had establishedSMTP and the ubiquitous Sendmail mail transport programas a uniform infrastructure for e-mail. The extension of theInternet protocol to the creation of intranets has largelyeliminated the use of proprietary corporate e-mail systems.E-mail TrendsThe integration of e-mail with HTML for Web-style formattingand MIME (for attaching graphics and multimediafiles) has greatly increased the richness and utility ofthe e-mail experience. E-mail is now routinely used withinorganizations to distribute documents and other resources.However, the addition of capabilities has also opened securityvulnerabilities. For example, Microsoft Windows andthe popular Microsoft Outlook e-mail client together providethe ability to run programs (scripts) directly fromattachments (files associated with e-mail messages). Thismeans that it is easy to create a virus program that will runwhen an enticing-looking attachment is opened. The viruscan then find the user’s mailbox and mail copies of itself tothe people found there. E-mail has thus replaced the floppydisk as the preferred medium for such mischief. (See computervirus.)Beyond security issues, e-mail is having considerablesocial and economic impact. E-mail has largely replacedpostal mail (and even long-distance phone calls) as a wayfor friends and relatives to keep in touch. As more companiesbegin to use e-mail for providing routine bills andstatements, government-run postal systems are seeing theirfirst-class mail revenue drop considerably. Despite the riskof viruses or deception and the annoyance of electronicjunk mail (see spam), e-mail has become as much a part ofour way of life as the automobile and the telephone.Further ReadingCostales, Bryan, and Eric Allman. Sendmail. 3rd ed. Sebastapol,Calif.: O’Reilly, 2002.Sendmail Consortium. Available online. URL: http://www.sendmail.org/. Accessed July 22, 2007.Shipley, David, and Will Schwalbe. Send: The Essential Guide toEmail for Office and Home. New York: Knopf, 2007.Song, Mike, Vicki Halsey, and Tim Burress. The Hamster Revolution:How to Manage Your Email Before It Manages You. SanFrancisco: Bennett-Koehler, 2007.embedded systemWhen people think of a computer, they generally think ofa general-purpose computing system housed in a separatebox, for use on the desk or as a laptop or hand-held device.However, the personal computer and its cousins are only thesurface of a hidden web of computing capability that reachesdeep into numerous devices used in our daily lives. Moderncars, for example, often contain several specialized computersystems that monitor fuel injection or enhance the car’s gripon the road under changing conditions. Many kitchen appliancessuch as microwaves, dishwashers, and even toasterscontain their own computer chips. Communications systemsranging from cell phones to TV satellite dishes includeembedded computers. Most important, embedded systemsare now essential to the operation of critical infrastructure