As computing has matured, the lines separating many of the traditional computing environments have blurred. Consider the "typical office environment." Just a few yuears ago, this environmnt consisted of PCs connected to a network, with servers profiding file and print services. Remote access was awkward, and porability was achieved by use of laptop computers.
Today, web technologies and increasing WAN bandwidth are stretching the boundaries of traditional c omputing. Companies establish portals, which provide web accessiblity to theiur internal servers. Network computers (or thin clients)-which are essentially terminals that understand web-based computing-are used in place of traditional workstationis where more security or easier maintenance is desired. Mobile computers can synchronize with PCs to allow very portable use of company information. Mobile devices can also connect to wireless networks and cellular data networks to use the company's web portal(as well as the myriad other web resources).
At home, most users once had a single computer with a slow modem connection to the office, the Internet, or both. Today, network-connection speeds once availabe only at great cost azre relatively inexpensive in many places, giving home users more access to more data. These fast data connections are allowing home computers to serve up we pages and to run networks that include printers, client PCs, and servers. Many homes use firewall to protect their networks from security breaches. Firewalls limit the communications between devices on a network.
In the latter half of the 20th century, computing resources were relatively scarce. (Before that, they were nonexistent!) For a period of time, systems were either batch or interactive. Batch systems processed jobs in bulk, with predetermined input from files or other data sources. Interactive systems waited for input from users. To optimize the use of the computing resources, multiple users shared time on these systems. These time-sharing systems used a timer and scheduling algorithms to cycle processes rapidly through the CPU, giving each user a share of the resources.
Traditional time-sharing systems are rare today. The same scheduling technique is still in use on desktop computers, laptaps, servers, and even mobile computers, but frequently all the processes are owned by the same user(or a single user and the operating system). User processes, and system processes that provide service to the user, are managed so that each frequently gets a slice of computer time. Consider the windows created while a user is working at the same time. Even a web broiwser can be composed of multiple processes, one for each website currently being visited, with time sharing applied to each web browser process.
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