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yo ur P C. At so me Web addresses, the f ile displays co ntent f o r every visito r, and at o thers (like
amazo n.co m), a f ile will co ntain pro grams that run o n the Web server to generate custo m co ntent
just f o r yo u. Yo u do n’t always type a path o r f ile name as part o f a Web address, but there’s always a f ile lurking
behind the scenes. A Web address witho ut a f ile name will lo ad co ntent f ro m a def ault page. Fo r
example, when yo u visit “go o gle.co m,” Go o gle auto matically pulls up a page called “index.html,” a
f ile that co ntains the Web page that displays the Go o gle lo go , the text entry f ield, the “Go o gle
Search” butto n, and so o n. Yo u might no t see it, but it’s there. Butterf ingers, beware! P ath and f ile names are case sensitive—amazo n.co m/ bo o ks is co nsidered to
be dif f erent f ro m amazo n.co m/ BOOKS. Mistype yo ur capital letters af ter the do main name and
yo u might get a 404 erro r (the very unf riendly Web server erro r co de that means the do cument
was no t f o und). IP Addresses and the Domain Name System: “Where Is It? And How Do We
The IP Address
If yo u want to co mmunicate, then yo u need to have a way f o r peo ple to f ind and reach yo u. Ho uses
and businesses have street addresses, and telepho nes have pho ne numbers. Every device
co nnected to the Internet has an identif ying address, to o —it’s called an IP (Internet pro to co l)
address. A device gets its IP address f ro m whichever o rganizatio n is currently co nnecting it to the Internet.
Co nnect using a lapto p at yo ur university and yo ur scho o l will assign the lapto p’s IP address.
Co nnect at a ho tel, and the ho tel’s Internet service pro vider lends yo ur lapto p an IP address.
Lapto ps and o ther end-user machines might get a dif f erent IP address each time they co nnect, but
the IP addresses o f servers rarely change. It’s OK if yo u use dif f erent IP addresses during dif f erent
o nline sess...
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This document was uploaded on 01/31/2014.
- Winter '14