Q.(A)

Concept and Intuition

In computer networks, devices need to connect to each other to communicate. This connection often happens through physical cables, and these cables need specific connectors to plug into ports on devices like computers, routers, and switches. To ensure that equipment from different manufacturers can connect and work together seamlessly, standards are crucial.

The "RJ" in RJ 45 refers to a series of such standardized network interfaces. These standards define not just the physical shape of the connector, but also the specific wiring pattern inside it. This ensures that when you plug a cable into a port, the correct electrical signals are sent to the correct pins, allowing data to flow properly. The term "Registered" signifies that these standards are officially defined and documented, historically by the US Federal Communications Commission (FCC), to ensure interoperability across the telecommunications industry.

Step-by-step Solution

1. Understanding "RJ": The prefix "RJ" stands for Registered Jack. This term originated from the US telephone system, where the FCC (Federal Communications Commission) established a series of "Registered Jack" standards. These standards specify the wiring patterns for connecting telecommunications equipment to a service provider's network. While initially for telephones, the concept extended to data networking.

2. Understanding "45": The number "45" in RJ 45 is a specific identifier within the Registered Jack system. It denotes a particular wiring configuration for an 8-position, 8-contact (8P8C) modular connector. This specific wiring standard is widely used for Ethernet connections in local area networks (LANs). …

The key idea behind XML is that it separates data from presentation. Unlike HTML, which uses predefined tags to display content (like <h1> for a heading), XML lets you create your own tags to describe what the data is. For example, you could have <book>, <title>, or <price> — tags that describe the content, not how it looks.

This makes XML incredibly flexible for data exchange between different systems, configuration files, and document storage. It follows a strict tree structure where every opening tag must have a closing tag, and elements must be properly nested.

1. The "Extensible" part — You are not limited to a fixed set of tags. You can invent any tag name that makes sense for your data. This is why it's called "extensible": the language can be extended to fit any domain.

2. The "Markup Language" part — Like HTML, XML uses angle brackets (< >) to mark up text. But XML is about structure and meaning, not visual formatting. A typical XML snippet looks like:

   <note>
     <to>Tove</to>
     <from>Jani</from>
     <heading>Reminder</heading>
     <body>Don't forget me this weekend!</body>
   </note>
   

   Here, the tags describe the parts of a note — who it's to, who it's from, the heading, and the body.

3. Strict rules — XML is very strict about syntax. Every tag must be closed, attributes must be quoted, and tags must nest properly. This strictness is what makes XML reliable for data exchange — computers can parse it without ambiguity. …

The story of ARPANET begins not with a single invention, but with a Cold War-era problem: how to connect far-flung research computers so that scientists could share resources and data, even if parts of the network were knocked out. The U.S. Department of Defense’s Advanced Research Projects Agency (ARPA, later DARPA) took up this challenge in the late 1960s.

The key idea was packet switching — breaking messages into small, independent chunks that could travel different routes and be reassembled at the destination. This was a radical departure from the old telephone-style circuit switching, where a dedicated line had to be kept open for the entire conversation. Packet switching made the network robust: if one path failed, packets could simply be rerouted.

The first ARPANET link was established in 1969 between the University of California, Los Angeles (UCLA) and the Stanford Research Institute (SRI). Soon, nodes at UC Santa Barbara and the University of Utah joined. By 1971, there were 15 nodes, and the network was growing rapidly.