৪৯তম বিসিএস ⎯ তথ্য ও যোগাযোগ প্রযুক্তি [২৮১]

Classification is a type of supervised learning where the goal is to assign input data to one of several predefined categories or classes. In this example, an email is classified into either the spam or not spam category.

Example:
In a spam filter, the system is trained on labeled data (emails labeled as "spam" or "not spam") and learns to classify new emails into one of these categories.

Source: Artificial Intelligence: A Modern Approach by Stuart Russell and Peter Norvig

Linear regression is a supervised learning algorithm used for predicting a continuous output (dependent variable) based on one or more input features. It models the relationship between the input variables and the output as a linear equation.

Example:
In a real estate pricing model, linear regression can predict the price of a house based on its features (e.g., size, location, number of rooms).

Source: Pattern Recognition and Machine Learning by Christopher Bishop

The net charge of an atom is determined by the difference between the number of protons (positive charge) and electrons (negative charge). In this case:

• 12 protons contribute +12 charge,
• 10 electrons contribute -10 charge,
• The net charge is +12 - 10 = +2.

Source: Physics for Scientists and Engineers by Raymond A. Serway and John W. Jewett

source: Introduction to Special Relativity by Robert Resnic

In the AC small-signal model of a diode, the diode is represented by a dynamic resistance, known as the small-signal resistance, which depends on the operating point (the current and voltage across the diode). This dynamic resistance is the reciprocal of the slope of the diode’s I-V characteristic at the operating point.

Example:
The small-signal resistance r_d can be calculated as r_d = V_T/I_D, where V_T is the thermal voltage (approximately 26mV at room temperature) and I_D is the DC operating current.

Source: Electric Circuits by James W. Nilsson and Susan A. Riedel

The Single Responsibility Principle (SRP) states that an object or class should have only one responsibility, and therefore only one reason to change. This helps ensure that objects are focused, maintainable, and easier to understand.

Example:
A UserAccount class should manage user details, but it should not handle email notifications. Sending emails should be handled by a separate EmailService class.

Source: Software Engineering: A Practitioner's Approach by Roger S. Pressman

The Waterfall model is a sequential development process where each phase (requirements, design, implementation, testing, maintenance) must be completed before moving on to the next phase. It is more rigid compared to Agile models.

Example:
In a Waterfall project, once the requirements phase is completed, no changes are expected, and the development team proceeds directly to design and then coding.

Source: Software Engineering: A Practitioner's Approach by Roger S. Pressman

In Design by Contract, a precondition is a condition that must be true before a method is called. It defines what is expected from the caller and ensures that the method can operate correctly under these conditions.

Example:
For a method that transfers funds from one account to another, the precondition might be that the source account must have sufficient balance to cover the transfer.

Source: Software Engineering: A Practitioner's Approach by Roger S. Pressman

In project management and software development, when something occurs that obstructs progress, such as Technical problems, Schedule delays and Resource shortages.
It is generally called an issue.

Issue: A problem that has already occurred.
Risk: A potential problem that might occur in the future.
Bug: Refers specifically to defects in software code, not general project delays.
Milestone: A planned point or checkpoint in the project schedule, not a problem.

Example:
• A server crashes during deployment, it's issue
• A developer falls ill causing a delay in code completion, it's issue
• Concern that a component may fail in the future, it's risk

Source: Software Engineering: A Practitioner's Approach by Roger S. Pressman

White-box testing, also known as structural testing, clear-box testing, or glass-box testing, involves testing the internal workings of an application. The tester has access to the internal code and focuses on the structure, logic, and flow of the software. It requires knowledge of the code and is used to verify the correctness of specific functions or modules.

Source: Software Engineering by Ian Sommerville

Dependency Injection (DI) is a design pattern that allows an object’s dependencies (services, resources, etc.) to be injected into it from the outside, rather than the object creating them itself. This reduces coupling and increases flexibility and testability.

Example:
In a web application, the OrderService might depend on PaymentGateway and ShippingService objects. By using DI, these dependencies are provided to the OrderService from an external source rather than being hard-coded.

Source: Design Patterns: Elements of Reusable Object-Oriented Software by Erich Gamma et al.

One of the key principles of the Agile Manifesto is to prioritize customer collaboration over negotiating contracts. This ensures that the development team stays responsive to changing customer needs and provides value through frequent feedback and adaptation.

Example:
In Agile methods like Scrum, the product is developed in iterative cycles (sprints), and the product backlog evolves based on regular feedback from the customer, enabling the software to adapt to changing requirements.

Source: Software Engineering by Ian Sommerville

Software Maintenance involves updating and improving a system after its initial release. One of the main challenges is adding new features or making changes while ensuring that the existing functionality is not broken or negatively impacted (i.e., backward compatibility).

Example:
In a web application, adding a new payment gateway should not disrupt existing checkout processes.

Source: Software Engineering: A Practitioner's Approach by Roger S. Pressman

Component-Based Software Engineering (CBSE) focuses on building software from reusable components, each providing a specific service or functionality. These components can be independently developed, tested, and integrated into the overall system.

Example:
In a CRM system, components like user authentication, customer database, and sales tracking can be developed separately and then integrated into the final system.

Source: Software Engineering: A Practitioner's Approach by Roger S. Pressman

Test-Driven Development (TDD) is a software development process where tests are written before the actual code. It ensures that each unit of functionality is tested and meets the expected requirements before implementation begins.

Example:
In TDD, you would first write a test for a new feature (e.g., a login function), then write the code to pass the test, and refactor the code while ensuring the test still passes.

Source: Software Engineering: A Practitioner's Approach by Roger S. Pressman

In the MVC architecture, the Controller acts as an intermediary between the Model (data) and View (user interface). It processes user input, updates the Model, and refreshes the View accordingly.

Example:
In a web application, when a user submits a form, the Controller processes the form data and updates the Model (e.g., saving the data to a database) and then updates the View (e.g., showing a confirmation message).

Source: Software Engineering: A Practitioner's Approach by Roger S. Pressman

Supervised learning is a new AI technique where algorithms learn from labeled data to make predictions or decisions. The model is trained on a dataset that includes input-output pairs, and it generalizes to predict outcomes for new, unseen data.

Example:
In image recognition, a supervised learning algorithm might be trained on a dataset of images labeled as either cats or dogs, and it will learn to classify new images based on the features it has learned.

Source: Pattern Recognition and Machine Learning by Christopher M. Bishop

Backtracking Search is particularly effective for constraint satisfaction problems (CSPs), where solutions need to satisfy a set of constraints. It incrementally builds solutions and backtracks when a constraint is violated, allowing it to efficiently explore possible solutions.

Example:
In Sudoku, backtracking would try placing numbers in each cell, and if a number violates the Sudoku rules, it backtracks and tries a different number.

Source: Artificial Intelligence: A Modern Approach by Stuart Russell and Peter Norvig

The normalization constant in probabilistic reasoning is used to ensure that the sum of all probabilities in a probability distribution adds up to 1. This is important in Bayesian inference to maintain the validity of the probability distribution.

Example:
When updating the probability of a hypothesis after observing new evidence, the normalization constant ensures that the total probability of all possible outcomes remains 1.

Source: Artificial Intelligence: A Modern Approach by Stuart Russell and Peter Norvig

Statistical Machine Translation (SMT) relies on the analysis of parallel corpora, which are sets of text in one language paired with the corresponding translation in another language. SMT uses statistical methods to determine the best translation by aligning words and phrases between languages.

Example:
In the phrase "I am learning NLP," SMT would align "I" with "Yo" (in Spanish), "am learning" with "estoy aprendiendo," and "NLP" with "NLP."

Source: Artificial Intelligence: A Modern Approach by Stuart Russell and Peter Norvig

The Naive Bayes classifier is a supervised learning algorithm commonly used for classification tasks, especially when the features are conditionally independent given the class. It works well for problems like spam detection, sentiment analysis, and document classification.

Example:
In a spam email classifier, the Naive Bayes algorithm classifies an email as spam or not spam based on word frequencies and class probabilities.

Source: Pattern Recognition and Machine Learning by Christopher M. Bishop

Supervised learning tasks involve learning from a labeled dataset. In this case, predicting a person’s age based on features like height and weight is a regression task, which is a type of supervised learning where the output is a continuous variable.

Example:
A supervised learning model can predict a person's age based on known data points (training data) where the input is their height and weight, and the output is their age.

Source: Artificial Intelligence: A Modern Approach by Stuart Russell and Peter Norvig

Support Vector Machines (SVM) are effective for fraud detection because they can classify transactions as fraudulent or non-fraudulent, even in high-dimensional data. SVMs work well with imbalanced datasets (where fraudulent transactions are much less frequent) by finding the optimal hyperplane that separates the classes.

Example:
SVM can be used in credit card fraud detection by analyzing features like transaction amount, location, and time to classify whether a transaction is legitimate or fraudulent.

Source: Pattern Recognition and Machine Learning by Christopher M. Bishop

Mean Absolute Error (MAE) is a common evaluation metric for regression models. It calculates the average of the absolute differences between the predicted values and the actual values. A lower MAE indicates a better model.

Example:
If a regression model predicts house prices and the actual price for a house is $300,000, but the model predicts $290,000, the absolute error is $10,000. MAE would average these errors across all data points.

Source: Pattern Recognition and Machine Learning by Christopher M. Bishop

Word2Vec is a natural language processing (NLP) model used for learning vector representations of words based on their context. It captures semantic relationships between words, allowing similar words to have similar vector representations.
Common applications of Word2Vec in NLP:
Word similarity: Word2Vec is frequently used to calculate the similarity between words by comparing their vector representations. For example, words like "king" and "queen" will have similar vectors in Word2Vec because they are related semantically.

Document classification: Word2Vec can be used for transforming words into vectors, which can then be aggregated (averaged or summed) to represent an entire document. This document vector can be used for classification tasks like categorizing documents into topics.

Sentiment analysis: In sentiment analysis, Word2Vec can represent words and phrases used in reviews or social media posts. The word vectors are used to capture the sentiment of the text, determining whether it is positive, negative, or neutral.

Word2Vec is not used in image recognition, which is an entirely different domain of machine learning, typically handled by models like Convolutional Neural Networks (CNNs). Word2Vec is specifically used for text data, not for processing images.

Source: Pattern Recognition and Machine Learning by Christopher M. Bishop

The Jacquard Loom, invented by Joseph Marie Jacquard in 1801, was the first device to use punch cards to control the pattern of weaving. The loom used cards with holes to represent different patterns, and these cards could be reused for different patterns. This idea of programmable control via punch cards was later adopted in computing.

Example:
The Jacquard Loom influenced early computer pioneers like Charles Babbage, who used the concept of punch cards for controlling his Analytical Engine.

Source: The History of Computing by Carl D. Murray

The Control Unit directs the flow of data between the CPU, memory, and peripherals. It fetches instructions from memory, decodes them, and signals the ALU and other components to execute the operations.

Example:
While running a program, the CU ensures that instructions are executed in the correct order and data is moved to the right registers.

Source: Computer Networks by Andrew S. Tanenbaum

Output devices allow the computer to communicate results to the user. A printer converts digital information into a physical paper output.

Example:
Printing a report from Microsoft Word produces a hard copy via the printer, making it an output device.

Source: Computer Networks by Andrew S. Tanenbaum

System software is responsible for managing and controlling the hardware components of a computer. It includes the operating system, device drivers, and utilities that facilitate hardware and software interaction.

Example:
Windows and Linux are examples of system software that manage resources like memory, processing power, and storage devices.

Source: Software Engineering by Ian Sommerville

Start with the binary number 110.
To convert binary to octal, group the binary number into sets of 3 bits from right to left (if necessary, pad the leftmost group with zeros).
110 becomes 110 (since it's already 3 bits).

Now, convert the 3-bit group to its octal equivalent,
110 (binary) = 6 (octal)
110 (binary) convert:
1×2^2+1×2^1+0×2^0=4+2+0=6
So, the binary number 110 is indeed equal to the octal number 6.

Using the Absorption Law in Boolean algebra, A+A⋅B=A. This law states that if A is true, the term A⋅B does not affect the result, so it simplifies to just A.

Example:
If A = 1, the expression A+A⋅B will always equal 1, regardless of the value of B.

Source: Digital Design by M. Morris Mano

An Adder is a fundamental arithmetic circuit in digital systems used to perform the addition of binary numbers. The simplest type is the half adder, which adds two single bits, while the full adder can add three bits (two input bits and a carry-in).

Example:
In the case of binary addition, adding 1 + 1 would result in a sum of 0 with a carry of 1.

Source: Digital Design by M. Morris Mano

The Control Unit (CU) is responsible for directing the operations of the computer's processor. It decodes instructions and manages the flow of data between various components like the ALU, registers, and memory.

Example:
When an instruction to add two numbers is received, the Control Unit sends signals to the ALU to perform the addition operation.

Source: Computer Organization and Architecture by William Stallings

The Session Layer (Layer 5) in the OSI model is responsible for establishing, maintaining, and terminating communication sessions between applications. It ensures that data is properly synchronized between communicating systems.

Example:
For a video conference, the Session Layer manages the session’s setup, data synchronization, and termination when the session ends.

Source: Computer Networks (4th Ed.) by Andrew S. Tanenbaum

The Link Layer (also known as the Network Access Layer) in the TCP/IP model is responsible for the physical transmission of data over network interfaces. It deals with the actual transmission of packets over physical media like Ethernet cables or wireless signals.

Example:
Ethernet operates at the Link Layer to send frames between devices in a local area network (LAN).

Source: Computer Networking: A Top-Down Approach by James Kurose and Keith Ross

In HDLC, the flag sequence (01111110) is used to mark the start and end of a frame. It helps the receiver identify where a frame begins and ends, ensuring proper synchronization of the data stream.

Example:
Every HDLC frame begins and ends with 01111110, ensuring that the receiver knows where the frame starts and finishes.

Source: Data and Computer Communications by William Stallings

IEEE 802.11 defines the standard for wireless local area networks (WLANs), commonly known as Wi-Fi. It includes specifications for how devices communicate over radio waves in a wireless LAN environment, covering aspects like radio frequencies, security, and data rates.

Example:
Wi-Fi networks in homes and offices use IEEE 802.11 standards to enable wireless communication between laptops, smartphones, and routers.

Source: Computer Networking: A Top-Down Approach by James Kurose and Keith Ross

IEEE 802.15 defines the Bluetooth standard for short-range wireless communication. Bluetooth operates within the 2.4 GHz frequency band and is designed for low-power, low-cost, short-range data exchange between devices.

Example:
Bluetooth is commonly used to connect devices like headphones, keyboards, and smartphones to other devices wirelessly over a short distance.

Source: Data and Computer Communications by William Stallings

WAN (Wide Area Network) spans large geographical areas, often connecting multiple cities or countries. The internet is the most well-known example of a WAN.

Example:
The internet, which connects millions of computers globally, is a typical WAN.

Source: Computer Networks by Andrew S. Tanenbaum

RARP (Reverse Address Resolution Protocol) is a network protocol that allows a device to obtain its IP address when only its MAC address (hardware address) is known. This is the reverse process of ARP (Address Resolution Protocol), which resolves an IP address to a MAC address.
A device with a known MAC address sends a RARP request to the network.
The request is sent to a RARP server, which looks up the MAC address in its database to find the corresponding IP address.
The server responds to the device with the appropriate IP address.

Example:
Consider a diskless workstation (a computer that doesn't have a hard disk and thus cannot store configuration settings like an IP address). This workstation has a MAC address but needs an IP address to communicate over the network. It sends a RARP request to a server, which responds with the appropriate IP address.

Source: Computer Networks by Andrew S. Tanenbaum

TCP is a connection-oriented, reliable transport layer protocol. It ensures the reliable delivery of data packets through acknowledgment and retransmission in case of lost packets. This makes it suitable for applications where reliability is crucial, such as web browsing and email.

Example:
In TCP, a three-way handshake is used to establish a connection between two devices before data transfer begins.

Source: Computer Networking: A Top-Down Approach by James Kurose and Keith Ross

Authentication is the process of verifying the identity of a user or device. One of the most common methods is using a password, which the user must provide to prove their identity.

Example:
A user logging into an online banking system must provide a password to authenticate their identity.

Source: Computer Networks by Andrew S. Tanenbaum

SNMP is used for monitoring and managing network devices such as routers, switches, and servers. It allows network administrators to gather information about the device’s status, performance, and configurations.

Example:
SNMP can be used to check if a router’s CPU utilization is high or if there are errors on a network interface.

Source: Computer Networks by Andrew S. Tanenbaum

A for loop is typically used for iterating a block of code a specific number of times. It consists of three parts: initialization, condition checking, and update. The loop continues as long as the condition evaluates to true.

Example:
In C, a for loop can be written as:

for(int i = 0; i < 5; i++) {
printf("%d ", i);
}

Source: Introduction to Programming in C by Robert Sedgewick,

The #include directive is a preprocessor directive in C that tells the preprocessor to include the contents of a header file in the program. It allows you to use library functions or user-defined code across multiple files.

Example:

#include <stdio.h> // Includes the standard input-output library
int main() {
printf("Hello, World! ");
return 0;
}

In this example, the #include <stdio.h> directive includes the standard input/output functions such as printf.

Source: C Programming Language by Brian W. Kernighan & Dennis M. Ritchie

The fopen function in C is used to open a file. The mode "w" is used to open a file for writing. If the file does not exist, it will be created; if it exists, it will be overwritten.

Example:
FILE *file = fopen("file.txt", "w"); // Opens file.txt for writing
fprintf(file, "Hello, World! ");
fclose(file); // Close the file after writing


Source: C Programming Language by Brian W. Kernighan & Dennis M. Ritchie

The graphics.h library in C is used for creating graphics in console-based applications. It provides functions to draw shapes, lines, and handle graphical output on the screen.
Example:

This code initializes a graphics window, draws a rectangle, and waits for user input before closing.

Source: Graphics Programming in C by T.S. Wormald.

C++ provides several classes for multi-threaded programming, including the thread class to create threads, mutex for managing synchronization, and condition_variable for thread communication.

Example:

In this example, a thread is created to run the printHello() function.

Source: C++ Primer by Stanley B. Lippman

A primary key is a column or set of columns in a table that uniquely identifies each row in that table. It ensures that no two rows have the same values in the primary key column(s).

Example:
In a students table, the student ID could be the primary key because it uniquely identifies each student.

Source: Database Management Systems by Raghu Ramakrishnan

The SELECT operation (σ) in relational algebra is used to select rows from a relation that satisfy a given condition. It is similar to the WHERE clause in SQL.

Example:
σ Age > 30 (Employee)
This operation selects all rows from the Employee relation where the Age is greater than 30.

Source: Database Management Systems by Raghu Ramakrishnan

The UPDATE statement is used to modify existing records in a table. You can specify which rows to update and the new values for specific columns.

Example:
UPDATE Employees
SET salary = 60000
WHERE EmployeeID = 1;

This query updates the salary of the employee with EmployeeID = 1 to 60,000.

Source: SQL in 10 Minutes, Sams Teach Yourself by Ben Forta

In database systems, common file organizations include:
Heap file organization: Records are stored in any order as they are inserted.
Sequential file organization: Records are stored in sorted order.
Hashed file organization: Uses a hash function to determine where records are stored based on a key.

However, relational file organization is not a standard term used for file organization; instead, relational databases use structures like tables and indexes to organize data.

Example:
Heap File Organization: Unsorted storage of data, where new records are appended at the end.
Sequential File Organization: Data is stored in a sequential manner, like ordered entries in a phone book.

Source: Database Management Systems by Raghu Ramakrishnan

The primary key is an attribute or a set of attributes used to uniquely identify a record within a table. It is not a specific storage structure. The primary key is used to create indexes or organize data but is not itself a form of storage structure. The other options, such as heap file storage, index file storage, and clustered file storage, are all valid storage structures.

Example:
Index file storage: This involves creating an index to improve the speed of data retrieval based on specific attributes (such as the primary key).
Heap file storage: As described earlier, records are stored in the order they are inserted.

Source: Database Management Systems by Raghu Ramakrishnan

B-tree indexing is widely used in database systems because it allows efficient searching of data, including range queries. B-trees keep the data sorted and allow quick access to both individual and range queries, making them useful for querying ranges of values, such as finding all employees with salaries between two values.

Example:
A B-tree index on the Salary column in an Employees table allows efficient retrieval of all employees whose salary is between 30,000 and 50,000.

Source: Database Management Systems by Raghu Ramakrishnan

Common join algorithms include:
Nested-loop join: A basic method where each row from one table is compared with each row from another table.
Merge join: Efficient for sorted data, where two tables are merged based on matching values in the join column.
Hash join: Uses a hash table to partition the data and match the join keys.
However, an inverted index join is not a standard join algorithm in relational query optimization.

Example:
Merge join is efficient when both tables are already sorted by the join column, as it can join the tables by scanning through them linearly.

Source: Database Management Systems by Raghu Ramakrishnan

The main drawback of paging is that page faults can cause overhead in system performance. When a page fault occurs, the system must access secondary storage (disk) to retrieve the required page, which is significantly slower than accessing memory. If page faults occur frequently (a condition known as thrashing), system performance can degrade.

Example:
If a system runs low on available memory and has to swap pages in and out of RAM constantly, the disk I/O caused by frequent page faults can lead to noticeable delays.

Source: Operating System Concepts by Abraham Silberschatz, Peter Baer Galvin, and Greg Gagne

In multi-level systems, deadlock detection is handled by examining the resource allocation graph (RAG) for cycles. Each node represents either a process or a resource, and edges represent resource allocation or request. A cycle in the graph indicates a deadlock, where processes are waiting for each other in a circular manner.

Example:
A system with multiple resources and processes can detect deadlock by identifying cycles in the allocation graph. If P₁ waits for R₁, P₂ waits for R₂, and R₃ waits for P₁, the system detects a cycle and concludes that a deadlock has occurred.

Source: Operating System Concepts by Abraham Silberschatz, Peter Baer Galvin, and Greg Gagne

Rollback is a deadlock recovery technique where a process is reverted to a previously saved state, usually one that is free from deadlock. This approach ensures that the process can be restarted and that resources are reclaimed in a way that avoids the deadlock situation.

Example:
If process P₁ is in a deadlock, it may be rolled back to a previous checkpoint or state, and the system can resume execution, allowing resources to be released and deadlock to be avoided.

Source: Operating System Concepts by Abraham Silberschatz, Peter Baer Galvin, and Greg Gagne

Common file attributes include the file name, size, type, creation date, modification date, and permissions. File color is not a standard file attribute in most operating systems, though some graphical file explorers might allow color-coding files for user convenience.

Example:
A file name might be document.txt, the file size might be 10MB, and the modification date might be 2023-10-10.

Source: Operating System Concepts by Abraham Silberschatz, Peter Baer Galvin, and Greg Gagne

Journaling is a technique used by modern file systems to ensure integrity. It involves keeping a log (or journal) of all changes made to the file system. If the system crashes unexpectedly, the file system can refer to the journal to recover and restore the file system to a consistent state.

Example:
NTFS uses journaling to keep track of changes, such as file writes, and ensures that incomplete operations are rolled back upon recovery from a crash.

Source: Operating System Concepts by Abraham Silberschatz, Peter Baer Galvin, and Greg Gagne

The direction of the force depends on whether the charges are like or opposite. If the charges have the same sign (both positive or both negative), they repel each other. If the charges have opposite signs (one positive and one negative), they attract each other.

Example:
Two positive charges will push each other away, while a positive charge and a negative charge will pull each other together.

Source: Fundamentals of Physics by David Halliday, Robert Resnick, and Jearl Walker

Gauss’s Law can be applied easily when there is high symmetry in the charge distribution. The three main types of symmetry are:
Spherical symmetry: For a point charge or uniformly charged sphere.
Cylindrical symmetry: For an infinitely long line of charge.
Planar symmetry: For an infinite plane of charge.
The symmetry allows the electric field to be constant on the Gaussian surface, making the integration simpler.

Example:
For a uniformly charged sphere, the electric field outside the sphere can be calculated by choosing a spherical Gaussian surface.

Source: Fundamentals of Physics by David Halliday, Robert Resnick, and Jearl Walker

The magnetic field B at a point located at a distance r from a long straight current-carrying wire is given by Ampere's Law, which is expressed as:
B= μ₀I /2πr
Where:
B is the magnetic field (in tesla, T),
μ₀ is the permeability of free space, μ₀=4×10⁻⁷ T⋅m/A,
I is the current (in amperes, A),
r is the distance from the wire (in meters, m).

Example:
If the current I=1A and the distance from the wire r=0.5m, the magnetic field at that point can be calculated using this formula.

Source: Fundamentals of Physics by David Halliday, Robert Resnick, and Jearl Walker

According to Lenz's Law, the induced current will flow in such a direction that it opposes the change in magnetic flux. If the magnetic flux through the coil is decreasing, the induced current will flow in a direction that creates a magnetic field to counteract the decrease, attempting to maintain the flux.

Example:
If the magnetic flux through a coil is decreasing due to the movement of a magnet, the induced current will create a magnetic field that tries to pull the magnet back, opposing the decrease in flux.

Source: Fundamentals of Physics by David Halliday, Robert Resnick, and Jearl Walker

The speed of a wave (v) on a string is given by the formula:
v = √( T/ μ )
where T is the tension in the string and μ is the mass per unit length (linear density) of the string. The wave speed increases with greater tension and decreases with greater mass per unit length.

Example:
A tighter string allows for faster wave propagation, while a heavier string slows down the wave.

Source: Fundamentals of Physics by David Halliday, Robert Resnick, and Jearl Walker

The wave equation v=fλ states that the speed of a wave v is the product of its frequency f and its wavelength λ. If both frequency and wavelength change such that the product remains constant, the wave speed v will stay the same. In some mediums, like sound or light waves, the wave speed is independent of frequency and wavelength (for certain types of waves in the medium).

Example:
In a string or a medium where the wave speed is constant, if the frequency increases, the wavelength must decrease proportionally to maintain the same speed.

Source: Fundamentals of Physics by David Halliday, Robert Resnick, and Jearl Walker

To calculate the energy consumed by an electrical device, we use the formula:
E=P×t
Where:
E is the energy consumed (in watt-hours, Wh),
P is the power consumed (in watts, W),
t is the time for which the device is used (in hours, h).

Given that,
Power, P = 100 W,
Time, t = 12 hours.

Now, substitute the given values into the formula:
E = 100×12
= 1200
∴ E=1200 Wh

The energy consumed by the light bulb is 1200 Wh

Source: Fundamentals of Electric Circuits by Alexander and Sadiku

A dependent current source is a source in which the value of the current depends on the current or voltage elsewhere in the circuit. For example, it may provide a current that is proportional to the voltage in another part of the circuit.

Example:
A dependent current source could supply a current of 5A if the voltage across another component is 10V.

Source: Fundamentals of Electric Circuits by Alexander and Sadiku

In a series circuit, the total voltage is divided among the resistors according to their resistance values. The voltage across each resistor in a series circuit can be calculated using Ohm’s Law and the voltage divider rule.
The voltage divider rule is:
Vx=V×Rx / R

Where,
Vx is the voltage across the resistor Rx,
V is the total voltage across the series combination,
Rx is the resistance of the resistor for which we are finding the voltage,
R is the total resistance of the series circuit.

Given that,
Resistor 1, R₁ = 5Ω,
Resistor 2, R₂ = 10Ω,
Total voltage, V = 30V.
The total resistance of the series circuit, R = R₁+R₂=5Ω+10Ω =15Ω

Now, substitute the given values into the formula:
V₁ = V×R₁ / R
= {30×10} / 15
= 300/15
= 20
∴ V₁ = 20V

The voltage across the 10Ω resistor is 20V.

Source: Fundamentals of Electric Circuits by Alexander and Sadiku

Norton’s Theorem states that any linear network can be simplified into an equivalent current source in parallel with an equivalent resistor. The equivalent current source is called the Norton current (I_N) and the resistor is the Norton resistance (R_N).

Example:
For a complex network, we can replace it with a Norton equivalent consisting of I_N (Norton current) and R_N (Norton resistance), making it easier to analyze current division.

Source: Fundamentals of Electric Circuits by Alexander and Sadiku

The voltage across an inductor is given by the formula:
V = L× (dI/dt)

Where,
V is the voltage across the inductor (in volts),
L is the inductance of the inductor (in henries, H),
(dI/dt) is the rate of change of current with respect to time (in amperes per second, A/s).

Given that,
Inductance (L) = 25 H
Rate of change of current (dI/dt) = 5 A/s

Now, substitute the given values into the formula:
V =25×5
= 125
∴ V = 125V
The voltage across the inductor is 125V

Source: Fundamentals of Electric Circuits by Alexander and Sadiku

To calculate power, we use the formula that,
P = E/t

Where,
P is the power (in watts, W),
E is the energy consumed (in joules, J),
t is the time (in seconds, s).

Given that,
Energy consumed (E) = 1000 J,
Time (t) = 25 s.

Now, substitute the given values into the formula:
P = 1000/25
= 40
∴ P = 40 W

So, the power consumed by the electric motor is 40 watts (W).

Sources: Fundamentals of Physics by Halliday, Resnick & Walker

An ideal diode is assumed to have zero voltage drop when forward biased (no resistance in the forward direction) and conduct infinite current when forward biased. It has no current flowing when reverse biased (ideal case).
Example:
For an ideal diode in a forward-biased circuit, the voltage across it would be zero, and it would conduct any current required by the circuit without resistance.

Source: Electric Circuits by James W. Nilsson and Susan A. Riedel

The common collector configuration, also known as an emitter follower, provides high current gain but has low voltage gain. It is primarily used for impedance matching, as it provides a low output impedance.

Example:
In an emitter follower circuit, the voltage across the output is almost the same as the input, but the current is amplified significantly.

Source: Electric Circuits by James W. Nilsson and Susan A. Riedel

Adding an emitter resistor R^E to a transistor circuit helps stabilize the operating point by providing negative feedback. This reduces the impact of changes in the transistor’s β and the effects of temperature variations, improving the thermal stability and overall circuit stability.

Example:
A common emitter amplifier with an emitter resistor helps ensure that the transistor operates in a stable region even if there are changes in the transistor's characteristics.

Source: Electric Circuits by James W. Nilsson and Susan A. Riedel

The electric field ( E ) at a point is defined as the force per unit charge experienced by a test charge placed at that point.
Mathematically,
E = F/q

Where,
F is the force and
q is the charge.

Given that,
Charge, q = 4μC = 4 × 10^-6 C
Force, F = 16 N

Now, Substitute the given values into the Mathematically formula:
E = 16/ ( 4 × 10^-6 )
= 4 × 10⁶
∴ E = 4 × 10⁶ N/C

The answer is 4 × 10⁶ N/C

Source: Fundamentals of Physics by David Halliday, Robert Resnick, and Jearl Walker

The common collector amplifier, also known as an emitter follower, has a voltage gain approximately equal to 1. It does not invert the signal and provides unity gain with positive voltage. The voltage across the load resistor is nearly the same as the input signal, making it suitable for impedance matching.

Example:
In a common collector amplifier, the input voltage is nearly the same as the output voltage, providing a voltage gain of 1.

Source: Electric Circuits by James W. Nilsson and Susan A. Riedel

In a JFET, the current flowing from the source to the drain is controlled by the gate-source voltage (V_GS). The gate is reverse biased, creating a depletion region in the channel, which restricts the current flow. A more negative gate-source voltage increases the width of the depletion region, thereby reducing the current.
Example:
When the gate-source voltage (V_GS) is zero, the channel is fully open, allowing maximum current to flow. As the voltage becomes more negative, the channel narrows, and the current decreases.

Source: Electronic Devices and Circuit Theory by Robert Boylestad

A pointer stores the memory address of another variable, meaning it points to a location in memory where data is stored. It allows indirect access to the value of the variable it points to.
Example:
A pointer to an integer stores the address of an integer. If the integer variable int x = 5; is at address 0x2000, a pointer int *ptr = &x; stores the address 0x2000.

Source: Structured Computer Organization by Andrew S. Tanenbaum

In a linked list, each node contains two parts: the data element and a pointer (address) to the next node in the list. This allows dynamic memory allocation and the ability to add or remove elements without contiguous memory space.
Example:
A singly linked list node might look like:
struct Node { int data; Node *next; };
Here, data stores the value, and next stores the address of the next node.

Source: Structured Computer Organization by Andrew S. Tanenbaum

A linked list is commonly used for implementing ADTs like queues, stacks, and deques that need dynamic insertion and removal of elements. Unlike arrays, linked lists do not require predefined memory allocation, and elements can be added or removed at any point in constant time.

Example:
A Queue ADT can be efficiently implemented using a linked list, where enqueue and dequeue operations can be performed in O(1) time complexity.

Source: Data Structures and Algorithms in C by Adam Drozdek

The Greedy Method can solve the fractional knapsack problem, where items can be broken down into smaller parts (fractions) and included in the knapsack. In this case, selecting items with the highest value-to-weight ratio first yields the optimal solution.

Example:
In the fractional knapsack problem, given a set of items with specific values and weights, the greedy algorithm will select items starting with the highest value/weight ratio, allowing fractional parts of the items.

Source: Introduction to Algorithms by Cormen, Leiserson, Rivest, and Stein

Modern microprocessors use multi-core designs and larger cache sizes to improve performance. Multi-core processors allow multiple tasks to be processed simultaneously, while large caches help reduce the time spent accessing slower main memory.

Example:
Intel Core i7 processors feature multi-core designs with large L3 caches, significantly improving overall system performance for multitasking and demanding applications.

Source: Digital Logic and Computer Design by M. Morris Mano

The 8086 microprocessor uses a multiplexed bus system, where the address bus and data bus share the same physical lines. The address is sent during the first part of the clock cycle, and the data is sent in the second part.

Example:
In the 8086 microprocessor, AD0-AD15 are multiplexed lines that carry both address and data, improving the efficiency of the bus system.

Source: Microprocessor Architecture, Programming, and Applications by Ramesh S. Gaonkar

Reflexive, symmetric, and transitive are common properties of relations in set theory. A deterministic relation is not a standard type of relation in set theory.
• A relation R on a set A is reflexive if every element of A is related to itself (i.e., (a, a) ∈ R for all a ∈ A).
• A relation R is symmetric if for all a, b ∈ A, whenever (a, b) ∈ R, then (b, a) ∈ R.
• A relation R is transitive if whenever (a, b) ∈ R and (b, c) ∈ R, then (a, c) ∈ R.

Example:
In the set A = {1, 2, 3}, the relation R = {(1, 1), (2, 2), (3, 3)} is reflexive.

Source: Discrete Mathematics and Its Applications by Kenneth H. Rosen

Set A is defined as the set of all even numbers in the set of natural numbers N.
A={x∈N: x is an even number}
The natural numbers (N) are {1, 2, 3, 4, 5, 6, 7, ...}, and the even numbers in this set are {2, 4, 6, 8, 10, ...}.

Set B is defined as the set of integers y∈Z that are less than 0.
B={y∈Z: y<0}
The integers (Z) include both positive and negative numbers, and all integers less than 0 are negative numbers, i.e., { -1, -2, -3, -4, ...}.

The intersection of A and B (A∩B) is the set of elements that are in both A and B.
• Set A contains only positive even numbers.
• Set B contains only negative numbers.
Since A only includes positive even numbers and B only includes negative numbers, there are no common elements between the two sets. Thus: A∩B={}

The intersection of A and B is the empty set {}.

Source: Discrete Mathematics and Its Applications by Kenneth H. Rosen

A power set contains all subsets of the original set, and its size is 2n, where n is the number of elements in the original set.
The power set of a set is defined as the set of all possible subsets of the original set, including the empty set and the set itself.
For the set A={1,2}, the subsets are:
        • ∅ (the empty set),
        • {1} (a subset containing only 1),
        • {2} (a subset containing only 2),
        • {1,2} (the set itself).

Thus, the power set of A is: P(A)={∅,{1},{2},{1,2}}

For A={1,2}, there are 2 elements, so the power set contains 2²=4 subsets.

Source: Discrete Mathematics and Its Applications by Kenneth H. Rosen

The Cartesian product of two sets, denoted by A×B, is the set of all ordered pairs where the first element is from set A and the second element is from set B.
Mathematically, it is defined as:
A×B={(a,b):a∈A and b∈B}

Given that,
Set A = {1, 2}
Set B = {a, b}

Now,
The Cartesian product A×B consists of all possible ordered pairs where the first element comes from A and the second element comes from B.
We can form the following pairs:
From 1 in A with each element in B: (1, a), (1, b).
From 2 in A with each element in B: (2, a), (2, b).

Thus, the Cartesian product A×B is:
A×B={(1,a),(1,b),(2,a),(2,b)}

Source: Discrete Mathematics and Its Applications by Kenneth H. Rosen

The number of ways to arrange n distinct objects is given by n!, which is the product of all positive integers from 1 to n. This is because there are n choices for the first object, n-1 for the second, and so on.

Example:
For n = 3, the number of permutations is 3! = 3 × 2 × 1 = 6, which corresponds to the sequences 123, 132, 213, 231, 312, 321.

Source: Discrete Mathematics and Its Applications by Kenneth H. Rosen,

A ring is an algebraic structure that consists of a set equipped with two operations: addition and multiplication. The operations must satisfy certain properties, including distributivity, where multiplication distributes over addition.

Example:
The set of integers Z with the usual addition and multiplication is an example of a ring.

Source: Discrete Mathematics and Its Applications by Kenneth H. Rosen

Given that,
Instruction Count = 1000
CPI (Cycles per Instruction) = 1
Clock Cycle Time = 2 ns
We know that,
CPU Time = Instruction Count × CPI × Clock Cycle Time
                = 1000 × 1 × 2  [ input the values ]
                = 2000
∴ CPU Time = 2000 ns
= 2μs  [1μs = 1000 ns ]

The answer of The CPU time is 2µs.

Source:  Digital Logic & Computer Design By M. Morris Mano.

In paging, both the virtual memory and physical memory are divided into fixed-size blocks. The blocks in virtual memory are called pages, and the blocks in physical memory are called frames. When a page is accessed, the corresponding frame is used to store the page.

Example:
If the virtual memory page size is 4KB and the physical memory frame size is also 4KB, when a page is needed, the system retrieves it and places it in a frame in physical memory.

Source: Computer Organization and Design by David A. Patterson and John L. Hennessy

The energy E stored in a capacitor is given by the formula,
E = 1/2 × CV²
Where,
E is the energy stored (in joules, J )
C is the capacitance (in farads, F)
V is the voltage across the capacitor (in volts, V).

Given that,
Capacitance, C=100μF=100×10⁻⁶ F,
Voltage, V=5 V.

Solution Here,
Substitute the given values into the formula,
E = 1/2  ×  100 × 10⁻⁶ ×  (5)²
   = 50 ×  10^-6 ×  25
  = 1250 ×  10^-6 
∴E = 1250 ×  10^-6 J
We can right, E = 1.25 mJ [1 m = 10^-3]

The energy stored in the capacitor is 1.25 mJ, so the correct answer is 1.25 mJ.

Source: Physics for Scientists and Engineers by Serway and Jewett

In IPv6, the Payload Length refers to the length of the data portion of the packet, excluding the header.
This is specified in the Payload Length field, which is a 16-bit field in the IPv6 header.
The IPv6 header consists of several fields, and the Payload Length field specifically indicates the length (in bytes) of the data that follows the header.
The Payload Length does not include the size of the IPv6 header itself (which is always 40 bytes).

IPv6 Header Format:
The IPv6 header contains the following fields:
i. Version (4 bits)
ii. Traffic Class (8 bits)
iii. Flow Label (20 bits)
iv. Payload Length (16 bits)
v. Next Header (8 bits)
vi. Hop Limit (8 bits)
vii. Source Address (128 bits)
viii. Destination Address (128 bits)

Example:
If the Payload Length field contains the value 1500, it means the data following the IPv6 header has a length of 1500 bytes.

Source: Computer Networking: A Top-Down Approach by James Kurose and Keith Ross

Given that,
I₁= 5A
I₂ =10A

Now, Kirchhoff’s Current Law states,
“The algebraic sum of currents entering a junction (or node) in an electrical circuit is equal to the sum of currents leaving the junction.”
Mathematically:
∑I_in = ∑I_out
∴ I₁+I₂ = I₃

Now, substitute the given values into the formula,
I₃ = 5A+10A
    =15A   
I₃ =15A
The right answer is 15A

Source: Electric Circuits by James W. Nilsson and Susan A. Riedel

The famous novel, The Bluest Eye, is written by - American author.

• The Bluest Eye:
- এটি Toni Morrison রচিত।
- এটি একটি novel.
- এটি ১৯৭০ সালে প্রকাশিত হয়।

• Toni Morrison ছিলেন একজন আমেরিকান Novelist, essayist এবং Editor.
- তাছাড়া তিনি Princeton University এর প্রফেসর ছিলেন।

তাঁর উল্লেখযোগ্য সাহিত্যকর্ম গুলো -
- Beloved,
- Song of Solomon,
- The Bluest Eye.

Source: Britannica.

বাংলাদেশের তত্ত্বাবধায়ক সরকার:
- বাংলাদেশের তত্ত্বাবধায়ক সরকার বাংলাদেশের একপ্রকারের শাসন ব্যবস্থা, যার অধীনে দুইটি নির্বাচিত সরকারের মধ্যবর্তী সময়কালে সাময়িকভাবে অনির্বাচিত ব্যক্তিবর্গ কোন দেশের শাসনভার গ্রহণ করে থাকে।
- বিএনপি সরকারের পদত্যাগের পর ১৯৯৬ সালে ত্রয়োদশ সংশোধনের মাধ্যমে সংবিধানে যোগ হয় তত্ত্বাবধায়ক সরকার পদ্ধতি।
- এই সংশোধনীর মাধ্যমে ১৯৯৬ সালে সাংবিধানিকভাবে তত্ত্বাবধায়ক সরকার ব্যবস্থা চালু হয়।
- বিচারপতি মুহাম্মদ হাবিবুর রহমান ছিলেন সেই তত্ত্বাবধায়ক সরকারের প্রধান উপদেষ্টা।
- উপদেষ্টা পরিষদের বাকিরা হলেন: ব্যারিস্টার সৈয়দ ইশতিয়াক আহমেদ, ড. মুহাম্মদ ইউনূস, অর্থনীতিবিদ ড. ওয়াহিদউদ্দিন মাহমুদ, অধ্যাপক মো. শামসুল হক, অধ্যাপক জামিলুর রেজা চৌধুরী, শেগুফতা বখত চৌধুরী, এ জেড এম নাছিরুদ্দিন, সৈয়দ মঞ্জুর এলাহী, অধ্যাপক নাজমা চৌধুরী ও মেজর জেনারেল (অব.) আব্দুর রহমান খান।
- এই তত্ত্বাবধায়ক সরকার মোট ৮৬ দিন ক্ষমতায় ছিল। এই সরকার ১৯৯৬ সালের ১২ জুন জাতীয় সংসদের নির্বাচনের তারিখ ঘোষণা করেন।
- অবশেষে বিপুল উৎসাহ ও উদ্দীপনা মধ্য দিয়ে ১৯৯৬ সালের ১২ জুন তত্ত্বাবধায়ক সরকারের অধীন প্রথম সপ্তম জাতীয় সংসদ নির্বাচন অনুষ্ঠিত হয়।

উল্লেখ্য,
- ১৯৯০ সালে সেনাশাসক হুসেইন মুহম্মদ এরশাদের পতনের পর জাতীয় নির্বাচন আয়োজন পর্যন্ত দায়িত্ব পালনের জন্য গঠন করা হয়েছিল নির্দলীয় প্রথম অন্তর্বর্তীকালীন সরকার।
- প্রধান বিচারপতি শাহাবুদ্দিন আহমেদের নেতৃত্বে ঐ সরকার গঠিত হয়েছিল।

এছাড়াও,
- ৩০ জুন, ২০১১ সালে পঞ্চদশ সংশোধনীর মাধ্যমে বাংলাদেশের সংবিধান থেকে 'তত্ত্বাবধায়ক সরকার ব্যবস্থা' বাতিল করা হয়।

উৎস: ইতিহাস ২য় পত্র, এইচএসসি প্রোগ্রাম, বাংলাদেশ উন্মুক্ত বিশ্ববিদ্যালয়।

তিস্তা মহাপরিকল্পনা:
- তিস্তা মহাপরিকল্পনা বাস্তবায়নে সহায়তা করবে চীন।

⇒ তিস্তা প্রকল্পের প্রথম পর্যায় বাস্তবায়নে ব্যয় হবে ৭৫ কোটি ডলার। এর মধ্যে চীন থেকে ঋণ চাওয়া হয়েছে ৫৫ কোটি ডলার। বাকিটা করা হবে সরকারি অর্থায়নে।
- চীনের রাস্ট্রদূত জানান, তিস্তা প্রকল্পের বিষয়টিতে অর্থ মন্ত্রণালয়ের অর্থনৈতিক সম্পর্ক বিভাগের (ইআরডি) সঙ্গে তারা কাজ করছেন।
- চীনের বিশেষজ্ঞ দল তিস্তা প্রকল্পের সম্ভাবনা যাচাই শেষে অক্টোবর, ২০২৫-এর মধ্যে তিস্তা মহাপরিকল্পনার ডিজাইন চূড়ান্ত হবে।
- ২০২৬ সালে এ প্রকল্পের কাজ শুরু করে ২০২৯ সালে শেষ করার লক্ষ্যমাত্রা নির্ধারণ করা হয়েছে।
- মহাপরিকল্পনায় তিস্তা নদীর ডান-বাম উভয় তীর ঘেঁষে ২২০ কিলোমিটার উঁচু গাইড বাঁধ, রিভার ড্রাইভ, হোটেল-মোটেল-রেস্তোরাঁ, পর্যটন কেন্দ্র, ১৫০ মেগাওয়াট সৌর বিদ্যুতকেন্দ্র, শিল্প-কারখানা, ইপিজেড, ইকোনমিক জোন, কয়েক লাখ হেক্টর কৃষি জমি উদ্ধার, বনায়ন ইত্যাদি রয়েছে।
- এ প্রকল্প বাস্তবায়ন হলে তিস্তা পাড় হয়ে উঠবে পূর্ব চীনের জিয়াংসু প্রদেশের সুকিয়ান সিটির মতো সুন্দর নগরী।

উৎস: i) প্রথম আলো।
ii) দৈনিক ইনকিলাব।

ড্রাগন ফল উৎপাদন:
- কৃষি সম্প্রসারণ অধিদপ্তরের তথ্য অনুযায়ী, ড্রাগন উৎপাদনের শীর্ষে আছে ঝিনাইদহ জেলা।
- ২০২৪-২৫ অর্থবছরে উৎপাদন হয় ৩২ হাজার ৭৬৮ মেট্রিক টন ড্রাগন।

• উৎপাদনের ২য় স্থানে রয়েছে যশোর। ২০২৪-২৫ অর্থবছরে উৎপাদন হয় ১২ হাজার ৫৫৩ মেট্রিক টন ড্রাগন। আর তৃতীয় শীর্ষ জেলা রাজশাহীতে উৎপাদন হয় ৪ হাজার ৪৭৭ মেট্রিক টন ড্রাগন।

⇒ ড্রাগন ফল মূলত আমেরিকার প্রসিদ্ধ একটি ফল যা বর্তমানে আমাদের দেশেও ব্যাপক জনপ্রিয়তা অর্জন করেছে। বাংলাদেশে সর্বপ্রথম ২০০৭ সালে থাইল্যান্ড, ফ্লোরিডা ও ভিয়েতনাম থেকে এই ফলের বিভিন্ন জাত আনা হয়। ড্রাগন ফলের গাছ এক ধরনের ক্যাকটাস জাতীয় গাছ। এই গাছের কোন পাতা নেই। ড্রাগন ফলের গাছ সাধারনত ১.৫ থেকে ২.৫ মিটার পর্যন্ত লম্বা হয়ে থাকে।

⇒ বর্তমানে বাংলাদেশ কৃষি গবেষণা ইন্সিটিউট (বারি) কতৃক উদ্ভাবিত ড্রগন ফলের নতুন জাতটি হলো বারি ড্রাগন ফল-১ যা দক্ষিণ -পূর্ব এশিয়াতে জনপ্রিয় ফল। এ ফলের আকার বড়, পাকলে খোসার রং লাল হয়ে যায় ,শাঁস গাঢ় গোলাপী রঙের, লাল ও সাদা এবং রসালো প্রকৃতির । ফলের বীজগুলো ছোট ছোট কালো ও নরম । একটি ফলের ওজন ১৫০ গ্রাম থেকে ৬০০ গ্রাম পর্যন্ত হয়ে থাকে।

উৎস: i) প্রথম আলো।
ii) কৃষি বাতায়ন।

OIC:
- ইসলামিক সহযোগিতা সংস্থা OIC.
- OIC এর পূর্ণরূপ The Organisation of Islamic Cooperation.
- ইসরাইল কর্তৃক আল আকসা মসজিদে আগুন ধরিয়ে দেওয়ার প্রেক্ষাপটে OIC গঠিত হয়।
- এটি মুসলিম দেশগুলোর একটি রাজনৈতিক জোট যা রাবাত সম্মেলনের মাধ্যমে গঠিত হয়।
- প্রতিষ্ঠার স্থান: মরক্কো।
- প্রতিষ্ঠিত হয়: ২৫ সেপ্টেম্বর, ১৯৬৯ সালে।
- সদর দপ্তর: জেদ্দা, সৌদি আরব।
- বর্তমান মহাসচিব: হুসাইন ইব্রাহিম তাহা (১২ তম)। (অক্টোবর, ২০২৫)
- মহাসচিবের মেয়াদ: ৫ বছর।
- অফিসিয়াল ভাষা: তিনটি (আরবি, ইংরেজি, ফ্রেঞ্চ)।
- বর্তমান সদস্য: ৫৭টি। (অক্টোবর, ২০২৫)

⇒ দক্ষিণ আমেরিকা অঞ্চলের দুটি দেশ OIC এর সদস্য।
• গায়ানা ও
• সুরিনাম।

- ইউরোপ মহাদেশের আলবেনিয়া OIC এর সদস্য।
- বাংলাদেশ ১৯৭৪ সালের ২২-২৪ ফেব্রুয়ারি পাকিস্তানের লাহোরে অনুষ্ঠিত OIC এর দ্বিতীয় শীর্ষ সম্মেলনে সর্বপ্রথম অংশগ্রহণ করে।

তথ্যসূত্র - OIC অফিসিয়াল ওয়েবসাইট।

কার্টাগেনা প্রটোকল (Cartagena Protocol):
- কার্টাগেনা প্রোটকলের পূর্ণনাম - The Cartagena Protocol on Biosafety to the Convention on Biological Diversity.
- কার্টাগেনা প্রটোকল জৈব-নিরাপত্তা বিষয়ক একটি আন্তর্জাতিক চুক্তি।
- এই চুক্তিটি কলম্বিয়ার কার্টাগেনাতে আলোচিত হয়।
- চুক্তি অনুমোদন - ২৯ জানুয়ারি, ২০০০ সাল।
- চুক্তি কার্যকর - ১১ সেপ্টেম্বর, ২০০৩ সাল।

তথ্যসূত্র - কনভেনশন অন বায়ো-ডাইভার্সিটি (CBD) ওয়েবসাইট।

জাতিসংঘ:
- জাতিসংঘের অর্থনৈতিক ও সামাজিক কমিশন (ECOSOC) এর অধীন ৫টি আঞ্চলিক কমিশন রয়েছে।

⇒ এগুলো হলো:
- এশিয়া ও প্রশান্ত মহাসাগরীয় অর্থনৈতিক ও সামাজিক কমিশন (ESCAP),
- পশ্চিম এশীয় অর্থনৈতিক ও সামাজিক কমিশন (ESCWA),
- ল্যাটিন আমেরিকা ও ক্যারিবীয় অর্থনৈতিক কমিশন (ECLAC),
- ইউরোপিয়ান অর্থনৈতিক কমিশন (ECE),
- আফ্রিকান অর্থনৈতিক কমিশন (ECA).

তথ্যসূত্র - UN ওয়েবসাইট।

ইউরোপীয় ইউনিয়ন (EU):
- বিশ্বের সবচেয়ে বড় অর্থনৈতিক জোট ইউরোপীয় ইউনিয়ন (EU)।
- এর সদর দপ্তর বেলজিয়ামের ব্রাসেলসে অবস্থিত।
- প্রতিষ্ঠাতা সদস্য: ৬টি দেশ।
- বেলজিয়াম, ফ্রান্স, জার্মানি, ইতালি, লুক্সেমবার্গ, নেদারল্যান্ডস।
- বর্তমান সদস্য: ২৭টি দেশ। (অক্টোবর, ২০২৫)
- সর্বশেষ সদস্য: ক্রোয়েশিয়া। (অক্টোবর, ২০২৫)
- সর্বশেষ ত্যাগকারী: ব্রিটেন (৩১ জানুয়ারি, ২০২০)।
- এটি ১৯৯৩ সালের ১ নভেম্বরে মাসট্রিচট চুক্তি স্বাক্ষরের মাধ্যমে প্রতিষ্ঠিত হয়েছিল।
- তখন থেকে এটি বিশ্বের বৃহত্তম ট্রেডিং ব্লকে পরিণত হয়।

তথ্যসূত্র - EU ওয়েবসাইট।

‘অপারেশন রাইজিং লায়ন':
- ইসরায়েল কর্তৃক ইরানে চালানো সামরিক অভিযানটির নাম 'অপারেশন রাইজিং লায়ন'।
- 'রাইজিং লায়ন' নামটি বাইবেলের একটি অনুচ্ছেদে সিংহের প্রতীকী পরাক্রমকে তুলে ধরে, ইসরায়েলের যুদ্ধ প্রস্তুতি এবং আত্মবিশ্বাসের প্রতীক।
- ১৩ জুন ২০২৫-এর ভোরে ইসরায়েলি বিমান বাহিনী ও গোয়েন্দা সংস্থা মোসাদ যৌথভাবে 'অপারেশন রাইজিং লায়ন' পরিচালনা করে।
- ইসরায়েল প্রথমে 'ড্রোন' দ্বারা ইরানের আকাশ প্রতিরক্ষা ব্যবস্থা দুর্বল করা, এরপর প্রধান পারমাণবিক ও সামরিক লক্ষ্যবস্তুতে বিমান হামলা করে।

উল্লেখ্য:
- এই হামলার জবাবে ইরান পাল্টা হামলা চালায়।
- এই হামলার নাম দেয়া হয় 'অপারেশন টু প্রমিজ থ্রি’।
- ইরান পাল্টা জবাবে শতাধিক ক্ষেপণাস্ত্র ও ড্রোন ছুড়ে।

তথ্যসূত্র - পত্রিকার রিপোর্ট।

IUCN:
- বিশ্ব জীববৈচিত্র্য সংরক্ষণবাদী সংস্থা (IUCN)।
- IUCN এর পূর্ণরূপ - International Union for the Conservation of Nature.
- প্রতিষ্ঠিত হয়: ১৯৪৮ সালে।
- সদর দপ্তর: গ্লান্ড, সুইজারল্যান্ড।
- এটি নিয়ে বিশ্বের ১৭০ টির অধিক দেশ কাজ করছে।
- উদ্দেশ্য: বিশ্বব্যাপী প্রাকৃতিক সম্পদ সংরক্ষণ করা।

তথ্যসূত্র - IUCN অফিসিয়াল ওয়েবসাইট।

IMF:
- IMF এর পূর্ণরূপ The International Monetary Fund.
- এটি আন্তর্জাতিক মুদ্রা তহবিল।
- প্রতিষ্ঠিত হয়: ১৯৪৪ সাল।
- সদর দপ্তর: ওয়াশিংটন ডিসি, যুক্তরাষ্ট্র।
- প্রতিষ্ঠাতা সদস্য: ৪৪টি।
- বর্তমান সদস্য: ১৯১টি। (অক্টোবর, ২০২৫)
- সর্বশেষ সদস্য: লিচেনস্টাইন। (অক্টোবর, ২০২৫)
- বর্তমান ব্যবস্থাপনা পরিচালক: ক্রিস্টালিনা জর্জিয়েভা। (অক্টোবর, ২০২৫)
- বাংলাদেশ সদস্যপদ লাভ করে: ১৯৭২ সালে।

তথ্যসূত্র - IMF অফিসিয়াল ওয়েবসাইট।

প্রশ্ন: P হচ্ছে Q এর পিতা কিন্তু Q, P এর ছেলে নয়। তাদের সম্পর্কটা কোন ধরনের?

সমাধান:
যেহেতু, P হচ্ছে Q এর পিতা কিন্তু Q, P এর ছেলে নয় সুতরাং Q হলো মেয়ে এবং P হচ্ছে পিতা।

সুতরাং, তাদের সম্পর্কটা মেয়ে-পিতা।

প্রশ্ন: নিচের চিত্রে কয়টি ত্রিভুজ আছে?

সমাধান:

একটি করে ফাঁকা ঘর নিয়ে ত্রিভুজ আছে - 1, 2, 3, 4, 5, 6, 7, 8 = ৮ টি
দুইটি করে ফাঁকা ঘর নিয়ে ত্রিভুজ আছে - 12, 34, 56, 78, 67, 58 = ৬ টি
চারটি করে ফাঁকা ঘর নিয়ে ত্রিভুজ আছে - 1267, 3456 = ২টি
সবগুলো ফাঁকা ঘর নিয়ে ত্রিভুজ আছে - 12345678 = ১ টি

সুতরাং, মোট ত্রিভুজ আছে = ৮ + ৬ + ২ + ১ = ১৭ টি

প্রশ্ন: একটি পানি ভর্তি বালতির ওজন ১৪ কেজি। বালতিটি অর্ধেক পানি পূর্ণ থাকলে তার ওজন হয় ৮ কেজি। খালি বালতির ওজন কত?

সমাধান:
দেওয়া আছে,
পানি ভর্তি বালতির ওজন = ১৪ কেজি
অর্ধেক পানি ভর্তি বালতির ওজন = ৮ কেজি
​
​অর্ধেক বালতি পানির ওজন = (১৪ - ৮) কেজি = ৬ কেজি
∴ ​পূর্ণ বালতি পানির ওজন = (৬ × ২) কেজি = ১২ কেজি
​
​আবার,
​পূর্ণ বালতি পানির ওজন + খালি বালতির ওজন = ১৪ কেজি
⇒ ​খালি বালতির ওজন = ১৪ - ​পূর্ণ বালতি পানির ওজন
​⇒ ​খালি বালতির ওজন = ১৪ - ১২ = ২ কেজি

প্রশ্ন: যদি ORANGE = SVERKI হয় তবে GRAPES = ?

সমাধান:
​যদি ORANGE = SVERKI হয় তবে GRAPES = KVETIW
​
​ORANGE শব্দটির বর্ণগুলো থেকে 4 ধাপ এগিয়ে পাওয়া যায়,
O(15) + 4 → S(19)
​R(18) + 4 → V(22)
​A(1) + 4 → E(5)
​N(14) + 4 → R(18)
​G(7) + 4 → K(11)
​E(5) + 4 → I(9)

​অনুরূপভাবে,
GRAPES শব্দটির বর্ণগুলো থেকে 4 ধাপ এগিয়ে গেলে KVETIW শব্দটি পাওয়া যায়। অর্থাৎ,
​G(7) + 4 → K(11)
​R(18) +4 → V(24)
​A(1) + 4 → E(5)
​P(16) + 4 → T(20)
​E(5) + 4 → I(9)
​S(19) + 4 → W(23)
​
অর্থাৎ নির্ণেয় শব্দটি হবে KVETIW

প্রশ্ন: যদি 7 + 3 = 410, 3 + 2 = 15, 6 + 5 = 111 হয়, তবে 8 + 4 = ?

সমাধান:
এখানে
7 + 3 = 410 ⇒ 7 - 3 = 4, 7 + 3 = 10
3 + 2 = 15 ⇒ 3 - 2 = 1, 3 + 2 = 5
6 + 5 = 111 ⇒ 6 - 5 = 1, 6 + 5 = 11

একইভাবে,
8 - 4 = 4, 8 + 4 = 12
সুতরাং, 8 + 4 = 412

প্রশ্ন: A দক্ষিণ দিকে মুখ করে ৪ কি. মি. হাঁটার পর বামদিকে ঘুরল এবং ৫ কি. মি. হাঁটল। আবার ডানদিকে ঘুরে ৮ কি. মি. হাঁটল। এখন যাত্রার স্থান থেকে সরাসরি দূরত্ব কত?

সমাধান:
প্রদত্ত তথ্যগুলোকে চিত্রের মাধ্যমে সাজিয়ে পাই,

এখন, উত্তর-দক্ষিণ দিকে- শুরুতে ৪ কি.মি. দক্ষিণ + পরে আরও ৮ কি.মি. দক্ষিণ = মোট ১২ কি.মি. দক্ষিণ
পূর্ব-পশ্চিম দিকে: শুধু পূর্ব দিকে ৫ কি.মি.

∴ সরাসরি দূরত্ব = √(১২^২ + ৫^২) = √(১৪৪ + ২৫)
= √১৬৯
= ১৩ কি.মি.

প্রশ্ন: (A) চিত্রটির আয়নায় প্রতিবিম্ব কেমন হবে?

সমাধান:


সুতরাং, সঠিক উত্তর (2) নং