Combined Bank Senior Officer Exam 15 May 2026 — Question Solution | সমন্বিত ব্যাংক (ব্যাংকার্স সিলেকশন কমিটি) সিনিয়র অফিসার নিয়োগ পরীক্ষা ২০২৬ — প্রশ্ন সমাধান

Correct answer: (c) AND

The output of an AND gate is 1 if and only if all of its inputs are 1; if any input is 0, the output is 0 (Kuphaldt). Texas Instruments' SN74HC08 datasheet ("Quadruple 2-Input AND Gates") agrees: its function table gives output H only when both inputs are H, and L if either input is L. Truth table: inputs 0,0 give 0; 0,1 give 0; 1,0 give 0; 1,1 give 1.
Other options: (a) OR — outputs 1 if any input is 1, and 0 only when all inputs are 0; (b) XOR — outputs 1 only when the inputs differ (01 or 10), so it gives 0 when both inputs are 1; (d) NAND — an AND followed by NOT: its output is 0 only when all inputs are 1, the exact opposite of AND.

Also know:

• A 2-input AND gate gives 1 for only one of its four input combinations, while an OR gate gives 1 for three of the four.
• NAND and NOR are universal gates: enough of either type can build any other gate.
• XOR can be built as an OR gate whose output is blocked by a NAND gate (through an AND gate) when both inputs are 1.

Sources: Lessons in Electric Circuits Vol. IV, Ch. 3: Logic Gates – T. R. Kuphaldt (ibiblio); SNx4HC08 Quadruple 2-Input AND Gates – Texas Instruments

Correct answer: (b) Half-duplex

In a half-duplex system two endpoints can exchange data in both directions, but only one direction is active at any given time; transmission and reception alternate.
Other options: (a) Simplex — carries data in one direction only; (c) Full-duplex — both parties transmit and receive simultaneously; (d) Multiplex — not a direction mode; it means transmitting two or more signals or messages by one system or circuit.

Also know:

• An ideal half-duplex link achieves at most half the throughput of an equivalent full-duplex link (IEEE).
• Cisco: collisions are normal on half-duplex Ethernet interfaces but must not be seen on full-duplex interfaces.
• In a duplex mismatch (one port half-duplex, the other full-duplex) the full-duplex side transmits without waiting its turn, and Cisco says the late collisions are seen on the half-duplex side; it names such a mismatch as a common cause of performance problems.

Sources: Half-duplex system – IEEE TechNav; Full-duplex system – IEEE TechNav; multiplex – Dictionary.com; Configure and Verify Ethernet Half/Full Duplex Auto-Negotiation – Cisco

Correct answer: (c) TCP

TCP provides a reliable, in-order, byte-stream service (RFC 9293). It detects losses with sequence numbers and errors with per-segment checksums, and corrects them by retransmission.
Other options: (a) UDP — sends messages with a minimum of protocol mechanism; delivery and duplicate protection are not guaranteed (RFC 768); (b) IP — does not provide a reliable communication facility: no acknowledgments, no retransmissions and no flow control (RFC 791); (d) ARP — converts a network-protocol (IP) address into a 48-bit Ethernet hardware address (RFC 826); it does not deliver application data.

Also know:

• TCP opens a connection with the three-way handshake (3WHS): SYN, SYN+ACK, ACK.
• UDP is protocol 17 in the IP header, and RFC 768 tells applications that need ordered, reliable delivery to use TCP.
• RFC 9293 (2022) is the current TCP specification; it obsoletes RFC 793.

Sources: RFC 9293: Transmission Control Protocol – IETF; RFC 768: User Datagram Protocol – IETF; RFC 791: Internet Protocol – IETF; RFC 826: An Ethernet Address Resolution Protocol – IETF