What is CSS? Features of CSS

CSS is the short form of Cascading which is a style sheet language used to describe the presentation of a document written in a markup language. In another word, CSS are used to describe the appearance of Web content.

Cascading Style Sheets - a language for describing the appearance of HTML-documents. Simply put, CSS language is designed to give the required appearance of HTML-documents. The purpose of CSS was to separate the description of the logical structure of the web page from her appearance. By using CSS web developer may specify the pages to separate its components and different typefaces and font sizes, colors elements padding elements from each other, arrangement of the individual blocks on the page, etc. Current version – CSS 3.

CSS basically provides style information to web documents.With CSS you can determine the position of the elements, color, font, margins, borders, lines, height, width, background images and much more. CSS is used to control presentation, formatting, and layout. Whereas HTML was the basic structure of your website, CSS is what gives your entire website its style.

CSS was a revolution in the world of web-design. Specific Benefits of CSS:

Control layout of many documents from one single style sheet;

Features of Cascading Style Sheets.

- The ability to manage any number of design documents from one single style sheet;

- The quality design of pages, which is supported by all browsers.

- Different views for different media (screen, print, etc...);

- CSS allows you to save time - you can, once creating CSS styles, use it with a variety of web pages

-Pages load faster - if you use CSS, you do not need to repeat the style of HTML

- More opportunities - in the CSS style attributes much more than with HTML

 

 

Tell about network and describe its topology (ring, bus, etc.)

A computer network is a group of computers that shares information across wireless or wired technology. Computer networks used to only be available for corporations but they are affordable for small businesses and individuals. Computer networking requires two computers, a protocol and the hardware to connect them.A computer network is a digital telecommunications network which allows nodes to share resources. In computer networks, computing devices exchange data with each other using connections between nodes.

These data links are established over cable media such as wires or optic cables, or wireless media such as WiFi.

  Network Topology is the schematic description of a network arrangement, connecting various nodes through lines of connection.

Topology refers to the pattern formed when computers are connected on a network.    1: Linear Bus 2. Ring 2: Star   3: tree topology

Bus topology is a network type in which every computer and network device is connected to single cable. When it has exactly two endpoints, then it is calledLinear Bus topology.

Features of Bus Topology: It transmits data only in one direction,

Every device is connected to a single cable.

Advantages of a Linear Bus Topology

- Easy to connect a computer or peripheral to a linear bus.

- Requires less cable length than a star topology.

- It is cost effective.

- Cable required is least compared to other network topology.

Disadvantages of Bus Topology

- Cables fails then whole network fails.

- If network traffic is heavy or nodes are more the performance of the network decreases.

- Cable has a limited length.

- It is slower than the ring topology.

Disadvantages of a Linear Bus Topology

- Entire network shuts down if there is a break in the main cable.

- Terminators are required at both ends of the backbone cable.

- Difficult to identify the problem if the entire network shuts down. Ring topology. It is called ring topology because it forms a ring as each computer is connected to another computer, with the last one connected to the first. Exactly two neighbours for each device.

AdvantagesofRingTopology

- Transmitting network is not affected by high traffic or by adding more nodes, as only the nodes having tokens can transmit data.

- Cheap to install and expand

DisadvantagesofRingTopology

- Troubleshooting is difficult in ring topology.

- Adding or deleting the computers disturbs the network activity.

- Failure of one computer disturbs the whole network.

STAR Topology. In this type of topology all the computers are connected to a single hub through a cable. This hub is the central node and all others nodes are connected to the central node.

   Features of Star Topology: Every node has its own dedicated connection to the hub,Hub acts as a repeater for data flow, Can be used with twisted pair, Optical Fibre or coaxial cable.

Advantages of a Star Topology

- Easy to install and wire.

- No disruptions to the network then connecting or removing devices.

- Easy to detect faults and to remove parts.

- Fast performance with few nodes and low network traffic.

Disadvantages of a Star Topology

- Requires more cable length than a linear topology.

- If the hub or concentrator fails, nodes attached are disabled.

- More expensive than linear bus topologies because of the cost of the

TREE Topology. It has a root node and all other nodes are connected to it forming a hierarchy. It is also called hierarchical topology. It should at least have three levels to the hierarchy.

AdvantagesofTreeTopology

- Extension of bus and star topologies.

- Expansion of nodes is possible and easy.

- Easilymanagedandmaintained.

- Error detection is easily done.

DisadvantagesofTreeTopology

- Heavily cabled.    - Costly.

- If more nodes are added maintenance is difficult.

Central hub fails, network fails.