computer science

Web server

Web server is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Web server rather than just read about it. In short: A web server is computer software that accepts requests via HTTP (the network protocol created to distribute web content) or its secure variant HTTPS. A user agent, commonly a web browser or web crawler, initiates communication by making a request for a web page or other resource using HTTP, and the server responds with the content of that resource or an error message.

Key takeaways

Web server belongs to computer science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Web server to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Web server from memory before moving on to harder problems.

Reference excerpt

A web server is computer software that accepts requests via HTTP (the network protocol created to distribute web content) or its secure variant HTTPS. A user agent, commonly a web browser or web crawler, initiates communication by making a request for a web page or other resource using HTTP, and the server responds with the content of that resource or an error message. A web server can also accept and store resources sent from the user agent if configured to do so. The hardware used to run a web server can vary according to the volume of requests that it needs to handle. At the low end of the range are embedded systems, such as a router that runs a small web server as its configuration interface. A high-traffic Internet website might handle requests with hundreds of servers that run on racks of high-speed computers. A resource sent from a web server can be a pre-existing file (static content) available to the web server, or it can be generated at the time of the request (dynamic content) by another program that communicates with the server software. The former usually can be served faster and can be more easily cached for repeated requests, while the latter supports a broader range of applications. Technologies such as REST and SOAP, which use HTTP as a basis for general computer-to-computer communication, as well as support for WebDAV extensions, have extended the application of web servers well beyond their original purpose of serving human-readable pages.

History

This is a very brief history of web server programs, so some information necessarily overlaps with the histories of the web browsers, the World Wide Web and the Internet; therefore, for the sake of clarity and understandability, some key historical information below reported may be similar to that found also in one or more of the above-mentioned history articles.

Initial WWW project (1989–1991) 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. The proposal titled "HyperText and CERN", asked for comments and it was read by several people. In October 1990 the proposal was reformulated and enriched (having as co-author Robert Cailliau), and finally, it was approved. Between late 1990 and early 1991 the project resulted in Berners-Lee and his developers writing and testing several software libraries along with three programs, which initially ran on NeXTSTEP OS installed on NeXT workstations:

a graphical web browser, called WorldWideWeb; a portable line mode web browser; a web server, later known as CERN httpd. Those early browsers retrieved web pages written in a simple early form of HTML from web servers using a new basic communication protocol that was named HTTP 0.9. In August 1991 Tim Berners-Lee announced the birth of WWW technology and encouraged scientists to adopt and develop it. Soon after, those programs, along with their source code, were made available to people interested in their usage. Although the source code was not formally licensed or placed in the public domain, CERN informally allowed users and developers to experiment and further develop on top of them. Berners-Lee started promoting the adoption and the usage of those programs along with their porting to other operating systems.

Fast and wild development (1991–1995) In December 1991, the first web server outside Europe was installed at SLAC (U.S.A.). This was a very important event because it started trans-continental web communications between web browsers and web servers. In 1991–1993, CERN web server program continued to be actively developed by the www group, meanwhile, thanks to the availability of its source code and the public specifications of the HTTP protocol, many other implementations of web servers started to be developed. In April 1993, CERN issued a public official statement stating that the three components of Web software (the basic line-mode client, the web server and the library of common code), along with their source code, were put in the public domain. This statement freed web server developers from any possible legal issue about the development of derivative work based on that source code (a threat that in practice never existed).

At the beginning of 1994, the most notable among new web servers was NCSA httpd which ran on a variety of Unix-based OSs and could serve dynamically generated content by implementing the POST HTTP method and the CGI to communicate with external programs. These capabilities, along with the multimedia features of NCSA's Mosaic browser (also able to manage HTML FORMs in order to send data to a web server) highlighted the potential of web technology for publishing and distributed computing applications.In the second half of 1994, the development of NCSA httpd stalled to the point that a group of external software developers, webmasters and other professional figures interested in that server, started to write and collect patches thanks to the NCSA httpd source code being available to the public domain. At the beginning of 1995 those patches were all applied to the last release of NCSA source code and, after several tests, the Apache HTTP server project was started. At the end of 1994, a new commercial web server, named Netsite, was released with specific features. It was the first one of many other similar products that were developed first by Netscape, then also by Sun Microsystems, and finally by Oracle Corporation. In mid-1995, the first version of IIS was released by Microsoft for Windows NT OS. This marked the entry, in the field of World Wide Web technologies, of a commercial developer and vendor that has played and still is playing a key role on both sides (client and server) of the web. In the second half of 1995, CERN and NCSA web servers started to decline (in global percentage usage) because of the widespread adoption of new web servers which had a much faster development cycle along with more features, more fixes applied, and more performances than the previous ones.

Explosive growth and competition (1996–2014)

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Web server

Start with the simplest possible case. Write down what Web server claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Web server before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Web server ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Web server

In research: Web server appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Web server in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Web server is common in secondary-school and first-year university syllabi. It links to neighbouring topics Data center technology, English inventions, Servers (computing), so understanding it makes those chapters shorter.
In everyday life: Look for Web server outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

Ask Teacher Smith questions about this articleOpens your AI tutor with a question about “Web server” →

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Web server in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Web server means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Web server out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Web server in simple terms?

Why does Web server matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Web server?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Web server.