Wednesday, March 21, 2007


While a computer may be viewed as running one gigantic program stored in its main memory, in some systems it is necessary to give the appearance of running several programs simultaneously. This is achieved by having the computer switch rapidly between running each program in turn. One means by which this is done is with a special signal called an interrupt that reason the computer to stop executing instructions periodically where it was and do something else instead. By remembering where it was executing preceding to the interrupt, the computer may return to that task later on.

If several programs are running "at the same time", then the interrupt generator may cause several hundred interrupts per second, causing a program switch each time. Since modern computers typically execute instructions several orders of magnitude faster than human perception, lots of programs may seem to be running at the same time even though only one is ever executing at any given instant. This method of multitasking is sometimes termed "time-sharing" since each program is allocated a "slice" of time in turn.

Halloween Costume

Monday, March 12, 2007


Web sites that are linked by a common theme or interest sometimes will join together to form Web rings. A Web ring is a community of Web sites linked one to another, so that visitors go from one site to the next until they return to the site where they started. A Web ring is an ideal way for Web users to find a wide variety of sites on a particular topic.

Most Web ring systems provide a listing or a directory of all the sites within a ring, which is known as the hub or list page. Such directories frequently include a description of each site and a link to let the visitors quickly go to a particular site within the ring.

Each member site within the Web ring also provides a navigation panel with links for "Next site," "Previous site," etc. that help the user move from site to site, skipping ones that are offline or going back to a site they visited previously. View a demonstration of a Web ring on The World of Webrings site.

Halloween Costumes