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The SPOKE hub distribution concept is used in the STAR topology in a computer network. Each host in a star network is linked to a CENTRAL hub. In its most basic form, a single hub serves as a message ROUTE. One of the most frequent computer network topologies is the star network.

Some of the benefits of star topology are as follows:

• It is simple to examine, set up, and change the star topology.
• The only nodes that have failed are those that have been affected. Other nodes are still operational.
• With a small number of nodes and little network traffic, high performance can be achieved.
• Adding, uninstalling, and transferring devices is simple in a Star topology.

Some of the drawbacks of star topology are as follows:

• The linked nodes are disabled if the Hub or concentrator fails.
• The expense of setting up a star topology is significant.
• Buses may experience significant delays due to heavy network load.
• The Hub's capacity determines performance.
• A damaged cable or a lack of adequate termination could bring the network offline.

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A C++ function to display all the nodes in a circular LINKED list is GIVEN below:

A few features of Hadoop are as follows:  

• OpenSource: Hadoop is free to use because it is open-source. Because it is an open-source project, the source code is available online for anybody to read and MODIFY according to their industry's needs.
• Fault Tolerance: Hadoop runs on commodity hardware (cheap computers) that can crash at any time. Data in Hadoop is duplicated across multiple DataNodes in a Hadoop cluster, ensuring data availability even if one of your systems fails. If a single machine has a technical problem, you can read all of the data from that machine. Because the data is copied or replicated by default, it can also be read from other nodes in a Hadoop cluster. Hadoop produces three copies of each file block by default and STORES them in various nodes. This replication factor is customizable and can be modified in the hdfs-site.xml file by modifying the replication attribute.
• Clusters with High Scalability: Hadoop is a model that is extremely scalable. A significant volume of data is split across several low-cost devices in a cluster and processed in parallel. According to the needs of the business, the number of these computers or nodes can be increased or decreased. Traditional RDBMS (Relational DataBase Management System) systems are incapable of scaling to massive amounts of data.
• Cheap and cost-effective: Unlike traditional Relational DATABASES, which require expensive hardware and high-end CPUs to deal with Big Data, Hadoop is open-source and leverages cost-effective commodity technology, resulting in a cost-effective paradigm. The difficulty with traditional Relational databases is that holding a large number of data is not cost-effective, thus businesses have begun to eliminate raw data, which may not result in the best business scenario. Hadoop offers two key cost advantages: it is open-source, which means it is free to use, and it employs commodity hardware, which is very inexpensive.
• High Availability: In a Hadoop cluster, fault tolerance ensures high availability. The availability of data on the Hadoop cluster is referred to as high availability. Because of fault tolerance, if one of the DataNodes fails, the data can be recovered from any other node where the data is replicated. The Hadoop cluster with the highest availability also has two or more NAME Nodes, i.e. Active NameNode and Passive NameNode, also known as standby NameNode, are two types of name nodes. If the Active NameNode fails, the Passive NameNode will take over and give the same data as the Active NameNode, which the user may easily use.
• Flexibility: Hadoop is built in such a way that it can efficiently handle any type of dataset, including structured (MySql Data), semi-structured (XML, JSON), and unstructured (Images and Videos). This implies it can analyse any type of data REGARDLESS of its form, making it extremely adaptable. It is extremely beneficial to organisations because it allows them to process enormous datasets quickly. As a result, businesses can utilise Hadoop to analyse important insights from data sources such as social media, email, and other sources. Hadoop's flexibility allows it to be used for log processing, data warehousing, fraud detection, and other tasks.

Global variables and Local variables can be DISTINGUISHED based on their features.

Global variables possess the FOLLOWING features:

• Variables DEFINED outside of a function or in a global space are known as global variables.
• If a variable in the function is ever GIVEN a new value, it is implicitly local, and we must explicitly designate it as 'global.' To make a variable global, we must declare it with the global keyword.
• From anywhere in the programme, any function can ACCESS and modify the value of global variables.

Local Variables possess the following features:

• Any variable declared within a function is referred to as a local variable. This variable only exists in local space; it does not exist in global space.
• If a variable receives a new value anywhere in the function, it is assumed to be local.
• The local body is the only part where these variables can be accessed.

The singleton pattern is a software engineering design pattern that RESTRICTS a class's instantiation to one "single" instance. When only one object is NECESSARY to COORDINATE system-wide actions, this is advantageous. The singleton is one of the most fundamental design patterns. Because creating a separate DB connection for each object could be expensive, we sometimes just REQUIRE one instance of our class, such as a single DB connection shared by multiple instances. Similarly, RATHER than building several managers, an application may have a single configuration or error manager that handles all issues.

The namespace is a fundamental idea for organising and structuring code that is particularly useful in large projects. However, if you're new to programming, this MAY be a difficult concept to grasp. As a result, we made an effort to MAKE namespaces more comprehensible. A namespace is a simple WAY to manage the names in a programme. It ensures that the names are DIFFERENT and won't be misunderstood. Python likewise EMPLOYS dictionaries to manage namespaces and keeps track of a name-to-object mapping, with names serving as keys and objects as values.

The term "functional PROGRAMMING" refers to a programming paradigm for dealing with PURE mathematical functions. Writing increasingly sophisticated and pure functions is the focus here. We may integrate a number of paradigms within a SINGLE PIECE of JavaScript code since JavaScript is a multi-paradigm language. Object-oriented, procedural, and functional programming paradigms can all be used with JavaScript at the same time. The fact that JavaScript is multi-paradigm and can interact with a range of programming languages is what MAKES it so appealing and powerful.

A callback function is a function that receives an input from another function and is then called from within the OUTER function to COMPLETE a routine or operation. Here's an illustration of a callback function in JavaScript:

Therefore, if we pass "New York" in the prompt, the output of this piece of code snippet will be "Welcome to New York!".

A system call is a way for a computer programme to REQUEST a service from the kernel of the operating system it is EXECUTING on. A system call is a program's way of interacting with the operating system. A system call is when a piece of software makes a request to the operating system's kernel. The Application Program Interface (API) is USED to provide services from the operating system to user programmes (API). It serves as a link between a process and the operating system, allowing user-level programmes to request services from the operating system. System calls are the sole way to GET into the kernel system. Any software that consumes resources must make USE of system calls.

Marshalling is the conversion of a memory representation of an object into a format that can be saved or transferred to other software applications. Marshalling is the process of converting an object into a serialised form that allows faraway objects to communicate with one other. The phrases SERIALISATION and marshalling are frequently USED interchangeably. The GOAL of marshalling is to have the same object that is present in one operating programme be present in another, i.e. a CLIENT object to be transferred to and present on the server. Serialization, for example, does not necessarily have this goal in mind because it is only concerned with converting DATA into a stream of bytes.

Storage Classes are used to define a variable's or function's properties. The scope, visibility, and durability of a variable are all characteristics that allow us to track its presence during the execution of a program. In the C programming language, there are four storage classes:

• Auto: All variables supplied inside a function or a block are stored in this class by default. Auto variables can only be used within the block/function in which they were defined; they cannot be used outside of that block/function (which defines their scope). They can be accessed outside of their scope, though, by using pointers that point to the memory address where the variables are stored. Whenever they are declared, they are given a garbage value by default.
• Extern: The storage class is external. The term "extern" simply denotes that the variable is defined outside of the block in which it is used. In essence, it is given a value in another block, which can subsequently be overwritten or updated in another block. An ordinary global variable can be made extern by using the 'extern' keyword before its declaration or definition in any function or block. This means that rather than creating a NEW variable, we're just accessing and using the global variable. The extern keyword can be used to make variables and functions more visible. The usage of extern in function declarations or DEFINITIONS is unnecessary because functions are visible throughout the programme by default. Its application is self-evident. When declaring a variable with extern, we are not really going to define it.
• Register: This storage class declares register variables, which are similar to auto variables in terms of functionality. The main difference is that the compiler will attempt to store these variables in the CPU's register if a free registration is available. If there are no free registers, the data is stored solely in memory. The register keyword is used to define a few variables that will be accessed frequently throughout a programme, allowing it to run faster. The address of a register variable cannot be accessed via pointers, which is a crucial detail to remember.
• Static: This storage type is used to define static variables, which are commonly UTILISED in C language programs. Static variables can preserve their value even after they've been removed from their scope! As a result, we can say that they are only initialised once and only exist till the program ends. Because they are not declared again, no new RAM is allocated. They have a limited scope, which is confined to the role that has been assigned to them. The program's global static variables can be accessed from ANYWHERE in the CODE. The compiler sets a value of 0 to these by default.

The UNIX kernel is the heart of the OPERATING system. It connects to the processor, memory, and I/O management, as WELL as the hardware DEVICES. The kernel manages user requests using system calls that shift the PROCESS from user to kernel space. Every TIME a user process makes a system call, such as read(), fork(), exec(), open(), and so on, a context switch happens. A context switch is a mechanism for changing the state of a process. The process can be stopped until the system call is finished, or it can continue and be notified when the system call is finished through a signal (nonblocking).

Virtual memory is a type of memory that is created on the storage device for a brief period of time. When a computer's RAM is drained as a result of numerous processes running at the same time, this happens. The operating system makes a portion of the storage disc available for use as RAM. Virtual memory is significantly slower than main memory because processing power is used by moving data around rather than performing instructions. The operating systems guide explains how memory is managed by the operating system. Latency increases when the computer must use virtual memory. To move data between RAM and virtual memory, the operating system uses SWAPPING. The operating system moves data from processes that aren't in use RIGHT now out of RAM and into virtual memory. When the PROCESS is required again, the data is copied BACK into RAM. Using virtual memory SLOWS down the machine since transferring to a hard disc takes much longer than reading and writing RAM.

 In C/C++, macros are preprocessor directives that are replaced at COMPILE time. As a result, a macro in a program is a named section of code. The compiler substitutes this name with the actual piece of code when it recognises it. The DRAWBACK of macros is that they are code changes rather than function calls. They also offer the ADVANTAGE of saving time when substituting IDENTICAL values.

All instances of the terms TEXT, EVEN, and SUMMATION in the sample code snippet below will be replaced with whatever is in their body.

OSI is an acronym for Open Systems Interconnection. The International Organization for Standardization (ISO) founded it in 1984 and It is a seven-layer architecture with separate functions for each tier. These seven layers work together to transport data across the globe from one person to another.

• Physical Layer: In the OSI reference model, the physical layer is the lowest layer. It is responsible for establishing a physical link between the devices. The physical layer stores bits of information. Its JOB is to send individual bits from one node to the next. This layer receives data and turns it into 0s and 1s before sending it to the Data Link layer, which reassembles the frame.
• Data Link Layer: The data link layer is in charge of message transport from one node to the next. This layer's primary function is to ensure that data transfers between nodes via the physical layer are error-free. The Data Link Layer is divided into two sublayers:
  • Control of Media Access (MAC)
  • Control of Logical Links (LLC)
• Network Layer: The network layer is in charge of data transfer between HOSTS that are linked to different networks. It also manages packet routing, which is the process of selecting the shortest path among a vast number of alternatives to send a packet. The SENDER and receiver's IP addresses are INCLUDED in the header by the network layer.
• Transport Layer: The transport layer provides services to the application layer, whereas the network layer provides services to the transport layer. In the transport layer, segments are the data units. It is in charge of delivering the entire message from start to finish. The transport layer recognises successful data transmission and re-transmits the data if a mistake is found.
• Session Layer: The Session Layer is responsible for creating connections, maintaining sessions, authenticating users, and guaranteeing security.
• Presentation Layer: The data from the application layer is obtained and processed in this layer so that it may be delivered across the network in the correct format.
• Application Layer: The Application layer is at the very top of the OSI Reference Model stack of layers, and it is implemented by network applications. These applications generate the information that must be transmitted via the network. This layer also serves as a window through which application services can connect to the network and display information to the user.

Socket programming is a method for allowing two network nodes to communicate with one ANOTHER. One socket (node) monitors traffic on a specific port at a GIVEN IP address, while the other socket connects to it. The server creates the listener socket while the client is connected to it.

The following are some of the benefits of Java Sockets:

• Sockets are adaptable and plentiful. For routine communications, socket-based programming is simple to build.
• Low network traffic is caused by sockets. Unlike HTML forms and CGI scripts, which build and DELIVER complete web pages for each new request, Java applets can merely send the updated data.

The following are some of the drawbacks of Java Sockets:

• Because a Java applet RUNNING in a Web browser can only connect to the machine from which it originated and nowhere else on the network, security constraints can be a pain at times.
• Despite all of Java's advantages, socket-based connections are confined to the transfer of raw data packets between programs. Both the client and the server must provide techniques for converting data into usable information.
• Socket-based systems are limited in their reusability since data formats and protocols are application-specific.

The bug life cycle, also CALLED the defect life cycle, is the PROCESS through which a defect advances through MULTIPLE phases over the course of its existence. This lifetime begins when a tester REPORTS an issue and ends when the problem has been fixed and will not recur. The following fault states can occur in a defect workflow.

• New: A new defect is referred to as "new" and given the status of New when it is first documented.
• Assigned: When a tester files a bug report, the tester's lead approves it and assigns it to the programming team.
• Open: The developer starts analysing and fixing the problem.
• Fixed: Once a developer has done a necessary code patch and confirmed it, he or she can mark an issue as "Fixed."
• Pending Retest: Once the issue has been resolved, the developer provides the tester with a unique code to retest the code. Because the software testing is still pending from the TESTERS, the status is "pending retest."
• Retest: At this stage, the tester retests the code to verify if the developer has repaired the problem, and the status is changed to "Re-test."
• Reopened: If the bug persists after the developer has fixed it, the tester changes the status to "reopened." The bug goes through the entire life cycle again.
• Verified: After the developer has fixed the bug, the tester re-tests it. The bug is repaired and the status is updated to "confirmed" if no bugs are detected in the software.
• Closed: The tester tags a bug as "Closed" when it is no longer existent.

A WEB application (or web app) is application SOFTWARE that runs on a web server, as OPPOSED to computer-based software APPLICATIONS that run locally on the device's operating system (OS). To ACCESS web applications, the user must utilise a web browser with an active network connection. The user ("client") accesses services from an off-site server hosted by a third party in these applications, which are designed on a client and server architecture. Regularly used web applications include webmail, online retail shopping, and online banking.

Schedulers are specialised computer programs that govern how processes are scheduled in various ways. Their primary responsibility is to determine which jobs should be entered into the system and which processes should be carried out.

The following are the three types of schedulers:

• Long Term Scheduler: A long term scheduler is ALSO KNOWN as a task scheduler. A long-term scheduler determines which applications are accepted for processing into the system. Before executing a process, it selects it from the ready queue and loads it into memory. For CPU scheduling, the process is loaded into memory. The job scheduler's primary goal is to deliver a well-balanced MIX of operations, including input/output and CPU-bound workloads. It also regulates how much multiprogramming is done. If the degree of multiprogramming remains constant, the average rate of process formation must be equal to the average rate of process departure from the system.
• Medium Term Scheduler: The medium-term scheduler is used to shift programs in the main memory. It frees up RAM that has been consumed by the processes. As a result, multiprogramming is reduced to a minimum. The SWAPPED out processes are managed by the medium-term scheduler.
• Short Term Scheduler: A short term scheduler is also known as a CPU scheduler. Its primary goal is to improve system PERFORMANCE in accordance with a set of predetermined criteria. It is the transition of a process from the ready to the operating state. The CPU scheduler picks one of the ready-to-run processes and allocates CPU time to it. Short term schedulers, often known as dispatchers, choose the next process to run.

DHCP is an acronym for Dynamic Host Configuration Protocol. It has a client and server architecture.

Given below are some of DHCP's perks or benefits:

• DHCP is simple to set up and automatically assigns IP addresses to request clients. As a result, the amount of time required to manually configure IP addresses will be brought down.
• The deployment will not result in any additional expenses.
• It is prevented that IP addresses can be assigned twice or incorrectly. As a result, no IP address disputes exist.
• It simplifies network administration.
• It can handle a wide range of scopes, including multicast and super scopes.
• It has a big advantage for mobile users because the newer network sends the relevant configuration parameters right away.

Given below are some of the disadvantages or drawbacks of DHCP:

• Due to the fact that DHCP packets cannot traverse routers, a relay AGENT is required to ENSURE that the DHCP server manages each and every COMMUNICATION for both the network segments. Relay agents accept broadcasted DHCP packets and these packets are forwarded by these agents as unicast packets towards the DHCP server. The relay agent should be configured with the DHCP server's IP address in this situation.
• The DHCP server may be a single point of failure in networks with only one configured DHCP server.
• Due to the LACK of a secure method for client authentication, the DHCP server can get unauthorised ACCESS to its IP addresses via the submission of credential details like DHCP client identifiers.
• The machine name remains the same on a new IP address being assigned.