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These phases are - Planning: This phase starts with the gathering of business requirements. In the subsequent spirals as the product matures, identification of system requirements and unit requirements are done in this phase. This also includes understanding of system requirements by continual communication between the customer and the analyst. At the end of the spiral the product is deployed. Design: Design phase starts with the design in the baseline spiral and involves architectural, logical design of modules, physical product design and final design in the successive spirals. Construct: Construct phase refers to development of the final software product at every spiral. In the spiral when the product is just thought and the design is being developed, a Proof of Concept (POC) is developed in this phase to get the users’ feedback. Then in the successive spirals with higher clarity on requirements and design a working model of the software called build is developed with a version number. These versions are sent to the users for feedback. Evaluation and Risk Analysis: Risk analysis includes identifying, estimating, and observing technical feasibility such as schedule slippage and cost overrun. After testing the build, at the end of first iteration, user evaluates the software and provides the feedback. Based on the customer assessment, development process enters into the next iteration and afterwards follows the linear approach to implement the feedback provided by the user. The process of iterations along the spiral carries on with throughout the life of the software. A web server is server software, or hardware dedicated to running this software, that can satisfy client requests on the World Wide Web. A web server can, in general, contain one or more websites. A web server processes incoming network requests over HTTP and several other related protocols.A user agent, commonly a web browser or web crawler, initiates communication by making a request for a specific resource using HTTP and the server responds with the content of that resource or an error message if unable to do so. The resource is typically a real file on the server's secondary storage, but this is not necessarily the case and depends on how the web server is implemented. While the major function is to serve content, a full implementation of HTTP also includes ways of receiving content from clients. This feature is used for submitting web forms, including uploading of files.Many generic web servers also support server-side scripting using Active Server Pages (ASP), PHP (Hypertext Preprocessor), or other scripting languages. This means that the behaviour of the web server can be scripted in separate files, while the actual server software remains unchanged. Usually, this function is used to generate HTML documents dynamically ("on-the-fly") as opposed to returning static documents. The former is primarily used for retrieving or modifying information from databases. The latter is typically much faster and more easily cached but cannot deliver dynamic content. Web servers can frequently be found embedded in devices such as printers, routers, webcams and serving only a local network. The web server may then be used as a part of a system for monitoring or administering the device in question. This usually means that no additional software has to be installed on the client computer since only a web browser is required (which now is included with most operating systems).The primary function of a web server is to store, process and deliver web pages to clients.[1] The communication between client and server takes place using the Hypertext Transfer Protocol (HTTP). Pages delivered are most frequently HTML documents, which may include images, style sheets and scripts in addition to the text content. In March 1989 Sir Tim Berners-Lee proposed a new project to his employer CERN, with the goal of easing the exchange of information between scientists by using a hypertext system.[2][3] The project resulted in Berners-Lee writing two programs in 1990:The world's first web server, later known as CERN httpd, which ran on NeXTSTEP.Between 1991 and 1994, the simplicity and effectiveness of early technologies used to surf and exchange data through the World Wide Web helped to port them to many different operating systems and spread their use among scientific organizations and universities, and subsequently to the industry. On the hardware side, a web server is a computer that stores web server software and a website's component files. (for example, HTML documents, images, CSS stylesheets, and JavaScript files) A web server connects to the Internet and supports physical data interchange with other devices connected to the web. On the software side, a web server includes several parts that control how web users access hosted files. At a minimum, this is an HTTP server. An HTTP server is software that understands URLs (web addresses) and HTTP (the protocol your browser uses to view webpages). An HTTP server can be accessed through the domain names of the websites it stores, and it delivers the content of these hosted websites to the end user's device. At the most basic level, whenever a browser needs a file that is hosted on a web server, the browser requests the file via HTTP. When the request reaches the correct (hardware) web server, the (software) HTTP server accepts the request, finds the requested document, and sends it back to the browser, also through HTTP. (If the server doesn't find the requested document, it returns a 404 response instead.) A static web server, or stack, consists of a computer (hardware) with an HTTP server (software). We call it "static" because the server sends its hosted files as-is to your browser.A dynamic web server consists of a static web server plus extra software, most commonly an application server and a database. We call it "dynamic" because the application server updates the hosted files before sending content to your browser via the HTTP server. For example, to produce the final webpages you see in the browser, the application server might fill an HTML template with content from a database. Sites like MDN or Wikipedia have thousands of webpages. Typically, these kinds of sites are composed of only a few HTML templates and a giant database, rather than thousands of static HTML documents. This setup makes it easier to maintain and deliver the content.To review: to fetch a webpage, your browser sends a request to the web server, which searches for the requested file in its own storage space. Upon finding the file, the server reads it, processes it as-needed, and sends it to the browser. Let's look at those steps in more detail. First, a web server has to store the website's files, namely all HTML documents and their related assets, including images, CSS stylesheets, JavaScript files, fonts, and video.Technically, you could host all those files on your own computer, but it's far more convenient to store files all on a dedicated web server because:For all these reasons, finding a good hosting provider is a key part of building your website. Examine the various services companies offer. Choose one that fits your needs and budget. (Services range from free to thousands of dollars per month.) You can find more details in this article. Second, a web server provides support for HTTP (Hypertext Transfer Protocol). As its name implies, HTTP specifies how to transfer hypertext (linked web documents) between two computers.A Protocol is a set of rules for communication between two computers. HTTP is a textual, stateless protocol.All commands are plain-text and human-readable. Neither the server nor the client remember previous communications. For example, relying on HTTP alone, a server can't remember a password you typed or remember your progress on an incomplete transaction. You need an application server for tasks like that. (We'll cover that sort of technology in other articles.)HTTP provides clear rules for how a client and server communicate. We'll cover HTTP itself in a technical article later. For now, just be aware of these things:On a web server, the HTTP server is responsible for processing and answering incoming requests Roughly speaking, a server can serve either static or dynamic content. Remember that the term static means "served as-is". Static websites are the easiest to set up, so we suggest you make your first site a static site.The term dynamic means that the server processes the content or even generates it on the fly from a database. This approach provides more flexibility, but the technical stack is more complex, making it dramatically more challenging to build a website.

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