Tips & Definitions:
Web hosting Making a Web site available on the Internet. Many ISPs host a few personal Web pages for an individual at no additional cost above the monthly service fee, but the address is subordinate to the ISP; for example, Multi-page, commercial Web sites are hosted at a very wide range of prices, and the customer's registered domain name is used. A single computer can hold dozens to hundreds of small Web sites, while a dedicated computer or multiple computers (from a handful to thousands) may be used for one large Web site. Entirely or Partially Managed Web hosting organizations can provide full service, including site design and programming as well as all e-commerce facilities. If customers wish to use their own servers and software, all their privately owned equipment can be co-located at the ISP, which provides power, Internet access and some level of management, which may be as little as ensuring that the servers are always running.
Host Yourself Many medium to large enterprises host their own Web sites and manage their own servers in their own facilities. Even home users can try, although many ISPs block traffic going to customer's Web server (see DDNS relay). See ISP, co-location and how to register a domain name. Web hosting is a service that provides Internet users with online systems for storing information, images, video, or any content accessible via the web. Web hosts are companies that provide space on a server they own for use by their clients as well as providing Internet connectivity, typically in a data center.
Types of hosting Hosting can be split up into six general types: free, shared, reseller, virtual private server, dedicated, and colocated. Free hosting: just about all the free web hosting available is extremely limited when compared to pay hosting. Free web hosts generally require their own ads on your site, only allow web-based uploading and editing of your site, and have very tight disk space and traffic limits. Still, most people get their start via free web hosting. Shared hosting: one's Web site is placed on the same server as several hundred other sites. A problem with another site on the server can bring all of the sites down. Shared hosting also brings with it some restrictions regarding what exactly can be done, although these restrictions are nowhere near as restrictive as for free hosting. Reseller hosting: designed for those who want to become Web hosts themselves. One gets a large amount of space and bandwidth that can be divided up among as many sites as the user wants to put on his account. A reseller account is placed on the same server with other reseller accounts, just like with shared hosting but there are fewer accounts.
Virtual Private Server hosting: Virtual Private Server technology enables one physical server to house several Virtual Environments which behave exactly like an isolated stand-alone server. This is often a much more affordable solution than a dedicated server, normally offering all the same benefits, such as root access. Dedicated hosting: With dedicated hosting, one gets a server of his own. They have no restrictions, except for those designed to maintain the integrity of the Web host's network (for instance, banning sites with adult content due to the increase risk of attack by hackers and grey legal issues for the ISP). Unless a separate plan is purchased from the host, the user is also generally on his own. This can be an expensive proposition, as the purchase of the dedicated server itself is generally far more expensive compared to shared hosting. Colocated hosting: This involves a server the user purchases himself and installs at the host's data center. Besides unmonitored reboots, the user must pay extra for many services dedicated hosting provides by default. Colocated hosting is generally chosen by people with server administration experience and those with more significant needs than which can be satisfied by dedicated or shared hosting. This is usually the most expensive and least cost effective option if you are not colocating many servers.
The Stored Program Concept The computer's ability to call in instructions and follow them is known as the "stored program concept." Instructions are copied into memory from a disk, tape or other source before any data can be processed. The computer is directed to start with the first instruction in the program. It copies the instruction from memory into its control unit circuit and matches it against its built-in set of instructions. If the instruction is valid, the processor carries it out. If not, the computer comes to an abnormal end (abend, crash). The computer executes instructions sequentially until it finds a GOTO instruction that tells it to go to a different place in the program. It can execute billions of instructions per second, using the same program logic on each new set of data brought in. Operations Overlap Input/output and processing are made to overlap. While one program is waiting for input from one user, the operating system (master control program) directs the computer to process data in another program. Large computers allow many input/output operations to occur simultaneously with processing. It can take hundreds of thousands of discrete machine steps to perform very routine tasks. Your computer could easily execute several million instructions to put a requested record on screen for you. Computer Generations First-generation computers, starting with the UNIVAC I in 1951, used vacuum tubes, and their memories were made of thin tubes of liquid mercury and magnetic drums. Second-generation systems in the late 1950s replaced tubes with transistors and used magnetic cores for memories (IBM 1401, Honeywell 800). Size was reduced and reliability was significantly improved.
Third-generation computers, beginning in the mid-1960s, used the first integrated circuits (IBM 360, CDC 6400) and the first operating systems and DBMSs. Online systems were widely developed, although most processing was still batch oriented using punch cards and magnetic tapes. Starting in the mid-1970s, the fourth generation brought us computers made entirely of chips. It spawned the microprocessor and personal computer. It introduced distributed processing and office automation. Query languages, report writers and spreadsheets put large numbers of people in touch with the computer for the first time. Even with the hundreds of millions of people using computers every day, we are still in the fourth generation. Some skill is still required to use the computer even if only to surf the Web and send e-mail. The fifth generation implies faster hardware and more sophisticated software that uses artificial intelligence (AI) routinely. Natural language recognition is a major component of the fifth generation. When you can have a reasonably intelligent conversation with the average computer, you will be in the fifth generation, perhaps in the 2015-2020 time frame.
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