বিপিএসসি নন-ক্যাডার সিএসই (বিষয়ভিত্তিক) MCQ প্রশ্ন সমাধান ২০২৫ — প্রশ্ন ও সমাধান

ব্যাখ্যা: Count-to-infinity is a problem in distance vector routing protocols like RIP. Link state routing protocol: Open Shortest Path First (OSPF) Intermediate System to Intermediate System (IS-IS) Shortest Path First Algorithm (Dijkstra algorithm)

ব্যাখ্যা: Managed switches support VLANs and per-port configuration.

ব্যাখ্যা: The network layer in the OSI model is responsible for determining how data is transferred between network devices and choosing the best path for data routing from source to destination. Protocols like IP (Internet Protocol) and routing algorithms such as RIP, OSPF, and BGP operate at this layer to ensure proper data forwarding between networks.

ব্যাখ্যা: A network bridge operates at Layer 2 (Data Link Layer) of the OSI model. It is used to connect two segments of a network and filter traffic based on MAC addresses. Unlike routers (Layer 3) which deal with IP addresses, bridges do not perform routing but do forward data intelligently at the frame level. Layer -1 :Physical Layer: hub, repeater. Layer-2: Switch, Bridge Layer-3: Router ,Gateway

ব্যাখ্যা: IP address classes are defined by the number of bits reserved for the network and host parts. Class C addresses have 24 bits for network and 8 bits for host. That gives 2⁸ = 256 total addresses per network. Since 2 addresses are reserved (one for the network ID and one for the broadcast address), only 254 addresses are available for hosts. Hence, Class C networks are used for small-sized networks.

ব্যাখ্যা: An IPv6 address is 128 bits (not bytes) in length. This provides a vastly larger address space compared to IPv4 (32-bit). IPv6 addresses are written as 8 groups of 4 hexadecimal digits separated by colons, e.g., 2001:0db8:85a3:0000:0000:8a2e:0370:7334.

ব্যাখ্যা: A VPN (Virtual Private Network) allows secure connections over a public network (like the internet) by creating an encrypted tunnel between the user's device and the network. This ensures privacy and security for private data transmission.

ব্যাখ্যা: A DHCP Discover message is sent using broadcast because the client initially doesn’t have an IP address and doesn’t know the DHCP server's address. So, it uses broadcast to reach all devices on the network.

ব্যাখ্যা: According to RFC 1918, the private IP ranges are: 10.0.0.0 – 10.255.255.255 172.16.0.0 – 172.31.255.255 192.168.0.0 – 192.168.255.255 Option d falls in the valid private address range.

ব্যাখ্যা: ARP (Address Resolution Protocol) is used to map an IP address to a MAC address in local networks. For reverse (MAC to IP), Reverse ARP (RARP) is used, although rarely today.

ব্যাখ্যা: Execution time is the time during which the CPU actively processes instructions of a job.

ব্যাখ্যা: Virtual memory allows the system to use disk space to simulate extra RAM, and paging is the method by which this is implemented.

ব্যাখ্যা: In operating systems, queues like ready or wait queues are implemented using linked lists because of their dynamic nature and efficiency in inserting/removing elements from any position without shifting elements like in arrays.

ব্যাখ্যা: System calls provide the interface through which a user process communicates with the operating system kernel. They allow programs to request OS services like reading from a file, creating a process, or allocating memory.

ব্যাখ্যা: In an operating system, when a process needs to use or release resources (e.g., memory, files, or devices), it does so by making a system call, which invokes OS services to handle the request safely and efficiently.

ব্যাখ্যা: Threads are the smallest units of CPU execution. An OS may create multiple threads to execute parts of a program concurrently. For multitasking, the OS may run multiple programs by creating multiple threads or processes.

ব্যাখ্যা: The primary key is the chosen unique identifier for records in a table, selected from the candidate keys.

ব্যাখ্যা: The SQL DROP command is used to completely remove a table or database structure.

ব্যাখ্যা: A Primary Key constraint ensures that: No two rows can have the same value in the primary key column(s). It also does not allow NULL values. Therefore, it guarantees uniqueness and row identity, effectively preventing duplicate rows.

ব্যাখ্যা: Second Normal Form (2NF) eliminates partial dependencies, meaning no non-prime attribute is dependent on a part of a composite primary key. • Partial Dependency মানে হলো কোনো non-prime attribute যদি composite primary key-এর আংশিক অংশের উপর নির্ভর করে, তাহলে সেটা partial dependency. ➤ 1NF (First Normal Form): • শুধুমাত্র এটুকু নিশ্চিত করে যে প্রতিটি অ্যাট্রিবিউটে atomic (অর্থাৎ indivisible) value আছে। • এখানেই repeat group, multi-valued attribute ইত্যাদি সরানো হয়। ➤ 2NF (Second Normal Form): • 1NF মেনে চলতে হবে। • সাথে কোনো partial dependency থাকা যাবে না। • অর্থাৎ, non-prime attributes must depend on the entire primary key, not a part of it. ➤ 3NF (Third Normal Form): • 2NF satisfied হতে হবে। • সাথে no transitive dependency থাকতে পারবে না। ➤ BCNF (Boyce-Codd Normal Form): • এটা 3NF-এর একটি বিশেষ কেস। • যেখানে প্রতিটি functional dependency-র left side অবশ্যই একটি super key হতে হবে। উদাহরণ: ধরা যাক, একটি relation আছে: Student_Course (StudentID, CourseID, CourseName) Primary Key: (StudentID, CourseID) এখানে যদি CourseName কেবলমাত্র CourseID-এর উপর নির্ভর করে, তাহলে এটি partial dependency, কারণ CourseName পুরো primary key (StudentID, CourseID)-এর উপর নির্ভর করছে না। এই অবস্থায় relation টি 2NF-এ নেই।