MEAN STACK DEVELOPMENT--(Unit-1)
DNS, or Domain Name System, serves as a fundamental infrastructure component of the internet, providing a way to map human-readable domain names to numerical IP addresses. The primary purpose of DNS is to facilitate the translation of easily memorable domain names (like www.example.com) into the numerical IP addresses (such as 192.168.1.1) that computers use to identify each other on a network.
Here are the key purposes and functions of DNS:
Human-Readable Naming:
- DNS enables users to access websites and services using user-friendly domain names instead of having to remember and use numerical IP addresses. This makes it much easier for people to navigate the internet.
Address Resolution:
- DNS acts as a distributed database that maintains a mapping between domain names and IP addresses. When a user enters a domain name in a web browser, the DNS system is queried to find the corresponding IP address.
Load Distribution:
- DNS can be used for load balancing by distributing incoming network traffic across multiple servers. This is achieved by associating multiple IP addresses with a single domain name and rotating the order of these addresses in DNS responses. This helps distribute the load and improve the performance and reliability of services.
Redundancy and Fault Tolerance:
- DNS supports redundancy and fault tolerance by allowing the association of multiple IP addresses with a single domain name. If one server or IP address becomes unavailable, DNS can route traffic to an alternative address, ensuring continuous service availability.
Hierarchical Structure:
- DNS has a hierarchical structure, with a decentralized system of name servers that work together to provide name resolution. This distributed nature makes the DNS system scalable and robust.
Name-to-Address Translation:
- DNS resolves domain names to IP addresses, allowing devices to communicate on the internet. This translation is essential for establishing connections and routing data between computers.
Email Routing:
- DNS is used in email systems for mail routing. It helps determine the mail server responsible for handling emails for a particular domain. This is specified in the DNS records called Mail Exchanger (MX) records.
Authentication (DNSSEC):
- DNS Security Extensions (DNSSEC) is an extension to DNS that adds an additional layer of security. It helps ensure the integrity and authenticity of DNS data, protecting against various attacks like DNS spoofing.
In summary, DNS plays a crucial role in making the internet more accessible and user-friendly by providing a decentralized and scalable method for translating domain names into IP addresses, facilitating seamless communication between devices on the internet.
2. Define HTTP and mention its primary function.
HTTP, or Hypertext Transfer Protocol, is the foundation of any data exchange on the Web. It is an application-layer protocol used for transmitting hypermedia documents, such as HTML. Developed within the context of the World Wide Web, HTTP facilitates communication between web browsers (clients) and web servers.
Primary Function of HTTP: The primary function of HTTP is to enable the transfer of hypertext, which includes text, images, videos, and other multimedia content, between a client and a server. It is the protocol that governs the way web browsers request web pages from servers and how servers respond to these requests.
Key features and aspects of HTTP include:
Stateless Protocol:
- HTTP is a stateless protocol, meaning that each request from a client to a server is independent and is not influenced by any previous requests. This simplifies communication and reduces the complexity of web transactions.
Request-Response Model:
- The communication between a client and a server follows a request-response model. A client sends an HTTP request to a server, specifying the desired action (e.g., fetching a webpage), and the server responds with the requested data or an indication of an error.
Text-Based:
- HTTP messages, both requests and responses, are text-based, making it human-readable. This characteristic facilitates debugging and understanding of the communication process.
Connectionless:
- Each request from a client to a server is an independent transaction, and the connection is typically closed after a response is provided. However, persistent connections (HTTP/1.1 and later) allow multiple requests and responses to be sent over a single connection, reducing latency.
Methods:
- HTTP defines several request methods or verbs, including GET (retrieve data), POST (submit data to be processed), PUT (update a resource), DELETE (delete a resource), and others. These methods define the action to be performed on a resource identified by a URL.
Uniform Resource Identifiers (URIs):
- HTTP uses URIs, commonly referred to as URLs (Uniform Resource Locators), to identify and locate resources on the web. URLs specify the protocol (HTTP or HTTPS), the domain, and the path to the resource.
Status Codes:
- HTTP responses include status codes that indicate the outcome of the request. Common status codes include 200 OK (successful request), 404 Not Found (resource not found), and 500 Internal Server Error (server error).
Cookies:
- HTTP supports the use of cookies, which are small pieces of data sent from a server and stored on the client. Cookies are often used to maintain state information between requests.
Overall, HTTP is a foundational protocol that enables the transfer of data on the World Wide Web, allowing users to access and interact with various resources, including web pages, images, videos, and other multimedia content.
3. What does FTP stand for, and how is it used in the context of the web?
FTP stands for File Transfer Protocol. It is a standard network protocol used to transfer files from one host to another over a TCP-based network, such as the internet. FTP is often employed for uploading or downloading files between a client (typically a computer) and a server (a remote system hosting files).
Here's how FTP is used in the context of the web:
File Transfer:
- The primary purpose of FTP is to facilitate the transfer of files between a client and a server. Users can upload files from their local system to a remote server or download files from a server to their local machine.
Authentication:
- FTP typically requires authentication to ensure that only authorized users can access files on a server. Users need to provide a username and password to log in to the FTP server.
Anonymous FTP:
- Some FTP servers allow anonymous access, where users can log in with a generic username (such as "anonymous" or "ftp") and provide their email address as the password. This is often used for public file repositories.
Directory Navigation:
- Users can navigate through the directory structure of the FTP server to locate and interact with different files and directories. Commands such as "cd" (change directory) and "ls" (list files) are commonly used for this purpose.
Two Modes of FTP:
- FTP operates in two modes: active mode and passive mode. In active mode, the client opens a random port for data transfer, while in passive mode, the server opens a random port. Passive mode is often used when the client is behind a firewall.
ASCII and Binary Transfer Modes:
- FTP supports two transfer modes: ASCII and binary. ASCII mode is suitable for text files, while binary mode is used for non-text files (binary files, images, executables) to ensure accurate file transfer.
Secure FTP (SFTP and FTPS):
- To enhance security during file transfers, variations of FTP exist, such as SFTP (SSH File Transfer Protocol) and FTPS (FTP Secure). These protocols add encryption to protect data during transmission.
Web Development:
- In the context of web development, FTP is often used by developers and administrators to upload website files to a web server. This allows them to publish updates, upload new content, or transfer website files between development and production environments.
While FTP has been widely used, it is important to note that it transmits data, including login credentials, in plain text, which poses security risks. In cases where security is a concern, alternatives like SFTP or FTPS, which provide encryption, are recommended.
4. Briefly describe the role of SMTP in internet communication.
SMTP, or Simple Mail Transfer Protocol, plays a crucial role in facilitating email communication on the internet. It is an application-layer protocol used for the transmission of electronic mail (email) between devices, specifically between email clients (senders) and email servers.
Here's a brief overview of the role of SMTP in internet communication:
Sending Emails:
- The primary function of SMTP is to send emails from the sender's email client to the recipient's email server. When you compose and send an email through your email client, SMTP is responsible for handling the process of sending that email to the recipient's email server.
Communication Between Mail Servers:
- SMTP operates in a client-server architecture. The email client (sender) acts as an SMTP client, and the email server (recipient's server) acts as an SMTP server. The client establishes a connection with the server to send the email.
Message Format and Transfer:
- SMTP defines the format of the email message and the rules for its transfer. It specifies how the email content, including the sender's address, recipient's address, subject, and message body, should be structured and transmitted.
Routing and Relaying:
- SMTP is responsible for routing the email through the appropriate network to reach the recipient's email server. In some cases, the email may pass through multiple SMTP servers (relaying) before reaching its final destination.
Delivery Confirmation:
- While SMTP itself doesn't guarantee the delivery of the email to the recipient's inbox, it provides a basic mechanism for delivery confirmation. The sender's SMTP server communicates with the recipient's SMTP server to acknowledge the successful receipt of the email.
Protocols for Email Retrieval:
- SMTP works in conjunction with other protocols for a complete email communication process. After an email is sent using SMTP, protocols like POP3 (Post Office Protocol 3) or IMAP (Internet Message Access Protocol) are used for retrieving emails from the recipient's server and delivering them to the recipient's email client.
Security Considerations:
- SMTP traditionally operated without encryption, transmitting data, including email content and login credentials, in plain text. To address security concerns, enhanced security measures like SMTP over TLS (Transport Layer Security) or STARTTLS have been introduced to encrypt the communication between the client and server.
In summary, SMTP is a fundamental protocol for sending emails over the internet. It defines the rules and procedures for the transfer of email messages between email clients and servers, facilitating communication and collaboration through electronic mail.
5. Compare and contrast HTML and HTML5.
HTML stands for Hyper Text Markup Language. It is used to design web pages using a markup language. HTML is the combination of Hypertext and Markup language. Hypertext defines the link between the web pages. A markup language is used to define the text document within tag which defines the structure of web pages. This language is used to annotate (at the note for computer) text so that a machine can understand it and manipulate text accordingly. Most of the markup (e.g. HTML) languages are human readable. The language uses tags to define what manipulation has to be done on the text. It is used for structuring and presenting the content on the web pages. HTML5 is the fifth version of HTML. Many elements are removed or modified from HTML5. There are many differences between HTML and HTML5 which are discussed below:
| HTML | HTML5 |
|---|---|
| It didn’t support audio and video without the use of flash player support. | It supports audio and video controls with the use of <audio> and <video> tags. |
| It uses cookies to store temporary data. | It uses SQL databases and application cache to store offline data. |
| Does not allow JavaScript to run in browser. | Allows JavaScript to run in background. This is possible due to JS Web worker API in HTML5. |
| Vector graphics is possible in HTML with the help of various technologies such as VML, Silver-light, Flash, etc. | Vector graphics is additionally an integral a part of HTML5 like SVG and canvas. |
| It does not allow drag and drop effects. | It allows drag and drop effects. |
| Not possible to draw shapes like circle, rectangle, triangle etc. | HTML5 allows to draw shapes like circle, rectangle, triangle etc. |
| It works with all old browsers. | It supported by all new browser like Firefox, Mozilla, Chrome, Safari, etc. |
| <HTML>,<Body> , and <Head> tags are mandatory while writing a HTML code. | These tags can be omitted while writing HTML code. |
| Older version of HTML are less mobile-friendly. | HTML5 language is more mobile-friendly. |
| Doctype declaration is too long and complicated. | Doctype declaration is quite simple and easy. |
| Elements like nav, header were not present. | New element for web structure like nav, header, footer etc. |
| Character encoding is long and complicated. | Character encoding is simple and easy. |
| It is almost impossible to get true GeoLocation of user with the help of browser. | One can track the GeoLocation of a user easily by using JS GeoLocation API. |
| It can not handle inaccurate syntax. | It is capable of handling inaccurate syntax. |
| Being an older version , it is not fast , flexible , and efficient as compared to HTML5. | It is efficient, flexible and more fast in comparison to HTML. |
| Attributes like charset, async and ping are absent in HTML. | Attributes of charset, async and ping are a part of HTML 5. |
There are many HTML elements which have been modified or removed from HTML5. Some of them are listed below:
| Element | In HTML5 |
|---|---|
| <applet> | Changed to <object> |
| <acronym> | Changed to <abbr> |
| <dir> | Changed to <ul> |
| <frameset> | Removed |
| <frame> | Removed |
| <noframes> | Removed |
| <strike> | No new tag. CSS is used for this |
| <big> | No new tag. CSS is used for this |
| <basefont> | No new tag. CSS is used for this |
| <font> | No new tag. CSS is used for this |
| <center> | No new tag. CSS is used for this |
| <tt> | No new tag. CSS is used for this |
Many new elements are added in HTML5 like nav, audio, figcaption, progress, command, time, datalist, video, figure, meter, data, section, time, aside, canvas, summary, rp, rt, details, wbr, header, footer, keygen, embed, article, hgroup, bdi, mark, output, source, track, section, ruby and many more.
6. Explain the significance of the <canvas>element in HTML5.
The <canvas> element in HTML5 is a powerful and versatile feature that allows developers to dynamically draw graphics, create animations, and manipulate images directly within a web page. It provides a bitmap-based drawing surface on which you can use JavaScript to render various visual elements, making it a key component for creating interactive and visually engaging web applications. Here are some significant aspects of the <canvas> element:
Dynamic Rendering:
- The
<canvas>element enables dynamic rendering of graphics using JavaScript. Developers can draw shapes, lines, text, images, and other visual elements on the canvas in response to user interactions, events, or other dynamic data.
- The
Drawing API:
- The canvas element provides a comprehensive 2D drawing API that includes methods for drawing paths, shapes, text, and images. Developers can control stroke and fill styles, set line widths, apply transformations, and manipulate pixel data directly on the canvas.
Animation:
- Through the combination of the
<canvas>element and JavaScript, developers can create animations by continuously updating the content of the canvas. This is achieved by redrawing the canvas at regular intervals, creating smooth and interactive animations.
- Through the combination of the
Interactivity:
- The canvas allows developers to capture user input, such as mouse clicks or keyboard events, and respond by updating the displayed graphics. This interactivity is crucial for building engaging and user-friendly web applications, games, and simulations.
Data Visualization:
- The canvas element is commonly used for data visualization, allowing developers to represent complex data sets graphically. Charts, graphs, and other visual representations can be dynamically generated and updated based on real-time data.
Image Manipulation:
- Developers can use the canvas for basic image manipulation tasks, such as cropping, resizing, and applying filters. Image data can be loaded onto the canvas, modified, and then displayed on the web page.
Compatibility:
- The
<canvas>element is supported by all modern web browsers, making it a cross-browser solution for creating dynamic graphics and animations. This ensures a consistent user experience across different platforms.
- The
Accessible Drawing Surface:
- The canvas provides a versatile and accessible drawing surface that can be utilized for a wide range of applications, from simple drawings to complex visualizations. It has become a fundamental tool for web developers aiming to create interactive and visually appealing content.
Here's a basic example of using the <canvas> element in HTML:
<!DOCTYPE html> <html> <body> <canvas id="GeeksforGeeks" width="200" height="100" style="border:1px solid black"> </canvas> </body> </html>
Output:
☐
CSS is used to add styles on web pages that contain HTML elements. There are three methods to add styles on web pages, these are – Inline, Internal, and External. In this article, we will see the differences between Inline, Internal, and External CSS styles.
Inline CSS: Inline CSS is a way of defining the styling of an HTML element by adding CSS rules directly to the element’s tag using the “style” attribute. It is used for quick and simple styling changes to specific elements, without creating a separate CSS file.
Syntax:
<p style="css_styles">
// Content
</p>
Example: In this example, we will change the color and font size of a paragraph element with the help of the “style” attribute.
- HTML
Output: Here, the “style” attribute has been added to the <p> tag and includes two CSS rules: “color” and “font-size”. The “color” rule is set to “red” and the “font-size” rule is set to “14px”. These rules will only apply to the specific paragraph element in which the “style” attribute has been added.
Inline CSS
Internal CSS: Internal CSS, also known as embedded CSS is a method of adding CSS rules directly to the head section of an HTML document. It involves using the <style> element to enclose the CSS code within the HTML document itself. Internal CSS is placed within the <head> section of the HTML document, typically after the document’s title and before any other content.
Syntax:
<style>
// CSS Properties
</style>Example:
- HTML
Output: In this example, the <style> element is used to enclose the CSS rules that apply to the h1 and p elements. Any styling applied with internal CSS is specific to that HTML document and cannot be used on other pages or websites.
Internal CSS
External CSS: External CSS is used to place CSS code in a separate file and link to the HTML document. To use external CSS, create a separate file with the .css file extension that contains your CSS rules. You can link this file to your HTML document using the “link” tag in the head section of your HTML document.
Syntax:
<head>
<link rel="stylesheet"
type="text/css" href="style.css">
</head>In this case, the “link” tag specifies the type of the file (CSS), the relationship between the HTML document and the CSS file (“stylesheet”), and the location of the CSS file (“href” attribute). The href attribute points to the URL or file path of your external CSS file.
Example: HTML code:
- HTML
Create a CSS file named styles.css and write all the codes in that CSS file
File name: style.css
- CSS
Output:
External CSS
Differences between Inline, Internal, and External CSS:
| Feature | Inline CSS | Internal CSS | External CSS |
|---|---|---|---|
| Location | It is used within HTML tag using the style attribute. | It is used within <head> section of HTML document. | It is used in a separate .css file. |
| Selector Scope | Affects a single element or a group of elements. | Affects multiple elements within the same HTML element. | Affects multiple HTML documents or an entire website. |
| Reusability | Not reusable. Styles need to be repeated for each element. | Can be reused on multiple elements within the same HTML document. | Can be reused on multiple HTML documents or an entire website. |
| Priority | Highest priority. Overrides internal and external styles. | Medium priority. Overrides external styles but can be overridden by inline styles. | Lowest priority. Can be overridden by both inline and internal styles. |
| File Size | Inline styles increase the HTML file size, which can affect the page load time. | Internal styles are part of the HTML file, which increases the file size. | External styles are in a separate file, which reduces the HTML file size and can be cached for faster page loads. |
| Maintainability | Not easy to maintain. Changes need to be made manually to each element. | Relatively easy to maintain. Changes need to be made in one place in the <head> section. | Easiest to maintain. Changes need to be made in one place in the external .css file. |
Inline CSS is used for quick and specific styling, internal CSS is used for multiple elements within the same HTML document, and external CSS is used for a more organized and scalable approach to styling, allowing for reusability and maintainability.
CSS: CSS stands for Cascading Style Sheet. Its main objective is to provide styling and fashion to the web page. CSS provides color, layout, background, font, and border properties. CSS features allow better content accessibility, enhanced flexibility, and control, as well as the specification of the characteristics of presentation.
CSS3: CSS3 stands for Cascading Style Sheet level 3, which is the advanced version of CSS. It is used for structuring, styling, and formatting web pages. Several new features have been added to CSS3 and it is supported by all modern web browsers. The most important feature of CSS3 is the splitting of CSS standards into separate modules that are simpler to learn and use.
Difference between CSS and CSS3:
| S.No. | CSS | CSS3 |
|---|---|---|
| 1 | CSS is capable of positioning texts and objects. | On the other hand, CSS3 is capable of making the web page more attractive and takes less time to create. CSS3 is backward compatible with CSS. |
| 2 | Responsive designing is not supported in CSS | CSS3 is the latest version, hence it supports responsive design. |
| 3 | CSS cannot be split into modules. | Whereas CSS3 can be breakdown into modules. |
| 4 | Using CSS, we cannot build 3D animation and transformation. | But in CSS3 we can perform all kinds of animation and transformations as it supports animation and 3D transformations. |
| 5 | CSS is very slow as compared to CSS3 | Whereas CSS3 is faster than CSS. |
| 6 | In CSS we have set of standard colors and it uses basic color schemes only. | Whereas CSS3 has a good collection of HSL RGBA, HSLA, and gradient colors. |
| 7 | In CSS we can only use single text blocks. | But in CSS3 we can use multi-column text blocks |
| 8 | CSS does not support media queries. | But CSS3 supports media queries |
| 9 | CSS codes are not supported by all types of modern browsers. | Being the latest version, CSS3 codes are supported by all modern browsers. |
| 10 | In CSS, designers have to manually develop rounded gradients and corners. | But CSS3 provides advanced codes for setting rounded gradients and corners |
| 11 | There is no special effect like shadowing text, text animation, etc. in CSS. The animation was coded in jQuery and JavaScript. | CSS3 has many advance features like text shadows, visual effects, and a wide range of font styles and colors. |
| 12 | In CSS, the user can add background colors to list items and lists, set images for the list items, etc. | Whereas CSS3 list has a special display property defined in it. Even list items also have counter reset properties. |
| 13 | CSS was developed in 1996. | CSS3 is the latest version of CSS and was released in 2005. |
| 14 | CSS is memory intensive. | CSS3 memory consumption is low as compared to CSS. |
New features of CSS3:
Combinator: CSS3 has a new General sibling combinator which matches up with sibling elements via the tilde (~) combinator.
CSS Selectors: CSS3 selectors are much advanced in comparison to simple selectors offered by CSS, and are termed as a sequence of easy to use and simple selectors.
Pseudo-elements: Plenty of new pseudo-elements have been added to CSS3 to give easy styling in depth. Even a new convention of double colons :: is also added.
Border Style: The latest CSS3 also has new border styling features like border-radius, image-slice, image-source, and values for “width stretch”, etc.
Background style properties: New features like background-clip, size, style, and origin properties have been added to CSS3.
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