Network Topology refers to the physical or logical arrangement of computers, servers, and network devices in a communication network. It defines how data flows between devices and affects performance, scalability, and fault tolerance.

1. Bus Topology

All devices are connected to a single central cable called the bus or backbone. Data travels in both directions along this cable. Each device has a unique address and only accepts data meant for it.

2. Star Topology — All devices connect to a central hub/switch. If one cable fails, only that device is affected.

3. Ring Topology — Devices form a circular path. Data travels in one direction until it reaches the destination.

4. Mesh Topology — Every device connects to every other device. Highly reliable but expensive.

5. Tree Topology — A hierarchical structure combining star and bus topologies.

6. Hybrid Topology — Combines two or more different topologies for flexibility.

The Central Processing Unit (CPU) is the brain of the computer. It performs all the processing tasks by executing instructions stored in memory. Modern CPUs contain billions of transistors and operate at speeds measured in gigahertz (GHz).

1. Fetch

The CPU retrieves the next instruction from the computer's RAM (Random Access Memory) using the Program Counter (PC), which keeps track of the address of the next instruction to be executed. The instruction is then loaded into the Instruction Register (IR).

2. Decode

The Control Unit (CU) interprets the fetched instruction and determines what operation needs to be performed. It breaks down the instruction into signals that direct other parts of the CPU, such as the Arithmetic Logic Unit (ALU).

3. Execute

The Arithmetic Logic Unit (ALU) performs the actual operation — whether it's arithmetic (addition, subtraction, multiplication, division) or logical (AND, OR, NOT, comparison) operations. For complex tasks, the CPU may use multiple cores working in parallel.

4. Store (Write Back)

The result of the execution is written back to memory (RAM) or stored in internal CPU registers for quick access. This completes the instruction cycle, and the CPU moves to the next instruction.

A Database is an organized, structured, and systematic collection of data stored electronically in a computer system. It is managed by a Database Management System (DBMS) such as MySQL, Oracle, Microsoft SQL Server, or PostgreSQL. Unlike simple file storage, a database allows users to efficiently store, retrieve, update, and delete data while maintaining data integrity and security.

Uses of Database in Office Administration:

• Store Large Amounts of Data: Offices can store thousands of employee records, client details, financial transactions, and inventory data in a compact digital format without physical paperwork.
• Data Retrieval and Management: Using SQL queries or search interfaces, administrators can instantly find specific records, generate reports, and analyze trends without manually searching through files.
• Manage User Access Rights: Databases implement role-based access control (RBAC). For example, a manager can view all records, while a clerk can only edit their assigned data. This ensures data security and accountability.
• Maintain Metadata: Metadata (data about data) helps track when records were created, modified, and by whom. This audit trail is essential for compliance and transparency in office operations.
• Indexing for Fast Searching: Database indexing creates pointers to data locations, allowing searches to complete in milliseconds even with millions of records — critical for customer service and decision-making.
• Backup and Recovery: Automated backup systems ensure that office data is protected against hardware failures, cyberattacks, or accidental deletion, with quick recovery options.
• Multi-User Collaboration: Multiple employees can simultaneously access and update the database without data conflicts, thanks to transaction management and locking mechanisms.

When an Ethernet connection fails, it disrupts all wired internet access. Systematic troubleshooting helps identify whether the issue is hardware-related, software-related, or due to the Internet Service Provider (ISP). Below is a step-by-step diagnostic process:

1. Power Cycle Modem/Router: Turn off the modem and router, unplug them from the power source, wait for 30 seconds, and then plug them back in. This clears temporary memory glitches and refreshes the network connection. Many connectivity issues are resolved by this simple restart.
2. Check Ethernet Cable: Inspect the RJ-45 cable for physical damage, bent pins, or loose connections. Try using a different cable or test the same cable on another device. A faulty cable is one of the most common causes of Ethernet failure.
3. Run Windows Network Troubleshooter: Navigate to Settings → Network & Internet → Status → Network Troubleshooter. This built-in tool automatically detects common issues like IP conflicts, driver problems, or misconfigured settings and attempts to fix them.
4. Verify IP Address using ipconfig: Open Command Prompt and type ipconfig /all. Check if the device has received a valid IP address (e.g., 192.168.x.x). If it shows 169.254.x.x, the DHCP server failed to assign an IP. Run ipconfig /release followed by ipconfig /renew to request a new IP.
5. Update Network Adapter Driver: Outdated or corrupted drivers can cause connection drops. Go to Device Manager, find the Ethernet adapter, right-click, and select "Update driver." Alternatively, download the latest driver from the manufacturer's website.
6. Contact ISP if Necessary: If all local troubleshooting fails, the issue may be with the ISP's infrastructure — such as a line outage, server maintenance, or account suspension. Contact their technical support with your diagnostic results for faster resolution.

A URL (Uniform Resource Locator) is the address used to access resources on the internet. The URL https://www.bb.org.bd can be broken down into several meaningful components, each serving a specific technical purpose:

• https:// — HyperText Transfer Protocol Secure: This is the secure communication protocol that encrypts data between the user's browser and the web server using SSL/TLS certificates. It ensures that sensitive information (like passwords and banking data) cannot be intercepted by hackers. The "S" stands for "Secure." Modern browsers mark HTTP sites as "Not Secure," making HTTPS essential for trust and SEO ranking.
• www. — Subdomain (World Wide Web): This is a conventional prefix that historically indicated a publicly accessible web server. While optional today, it remains widely used for consistency and branding. Other subdomains might include mail., ftp., or blog., each pointing to different services on the same domain.
• bb — Second-Level Domain (SLD): This is the unique, memorable name chosen by the organization. "bb" stands for Bangladesh Bank, the central bank of Bangladesh. The SLD is registered through domain registrars and must be unique within its top-level domain.
• .org — Generic Top-Level Domain (gTLD): Originally intended for non-profit organizations, .org is now used by various entities including government bodies, educational institutions, and community groups. It conveys credibility and public-service orientation. Other gTLDs include .com (commercial), .net (network), and .edu (education).
• .bd — Country Code Top-Level Domain (ccTLD): This two-letter code represents Bangladesh. It is managed by the Bangladesh Telecommunication Company Limited (BTCL). ccTLDs help identify the geographical origin of a website and can improve local search engine rankings. Examples: .in (India), .uk (United Kingdom), .us (USA).

(i) CAD (Computer-Aided Design)

CAD refers to the use of specialized software to create, modify, analyze, and optimize designs in both 2D and 3D formats. It is widely used in engineering, architecture, automotive design, and manufacturing industries. Popular CAD software includes AutoCAD, SolidWorks, and CATIA. CAD enables designers to visualize products before physical prototyping, simulate stress tests, and generate precise technical drawings with exact measurements. It dramatically reduces design time, minimizes errors, and allows easy iteration of concepts.

CAL (Computer-Aided Learning / Computer-Assisted Learning)

CAL is the integration of computer technology into the teaching and learning process to enhance educational outcomes. It includes interactive tutorials, simulations, educational games, virtual labs, and e-learning platforms like Moodle and Khan Academy. CAL supports personalized learning by allowing students to progress at their own pace, provides instant feedback, and makes complex subjects more engaging through multimedia content. It is especially valuable in distance education and for students with different learning abilities.

(ii) Cookies

Cookies are small text files (typically 4KB or less) that websites store on a user's device (computer, tablet, or smartphone) through the web browser. They are created when a user visits a website and are used to remember information such as login credentials, shopping cart items, language preferences, and browsing history. There are different types of cookies:

While cookies improve user experience by enabling personalization, they also raise privacy concerns. Modern browsers allow users to block or delete cookies, and regulations like GDPR require websites to obtain consent before storing non-essential cookies.

Trojan Horse

A Trojan Horse is a type of malware that disguises itself as legitimate, harmless, or even useful software to trick users into installing it. Unlike viruses, Trojans do not self-replicate; instead, they rely on social engineering tactics. Once activated, a Trojan can perform various malicious actions:

• Steal sensitive data such as passwords, banking details, and personal files.
• Create backdoors that allow hackers to remotely control the infected system.
• Install additional malware like ransomware or spyware.
• Log keystrokes to capture everything the user types.
• Use the infected computer as part of a botnet for distributed denial-of-service (DDoS) attacks.