IEMCET computing preparation: Multiplexers and selection bits — practice worksheet with answers

How to use this worksheet

This independent worksheet checks multiplexers and selection bits with a new problem, an explanation task and an interleaved related skill. It is not an official IEM question paper, a difficulty forecast or a prescribed timed examination.

Write an attempt first, then compare your method with the visible answers. Record whether a miss came from interpretation, a missing concept, execution or a condition you overlooked.

Question 1: apply the topic

How many inputs can four selector bits distinguish?

Answer and checking point

Sixteen.

Trace a small example and a boundary case. Distinguish correctness from complexity, a necessary condition from a sufficient one, and declared constraints from coincidences in sample data. Check whether the question asks for an exact count, a bound or a qualitative property.

Question 2: diagnose an approach

Explain why the following warning matters and identify the correction it calls for: The selector-bit count is logarithmic in the input count, not equal to it.

Model checkpoint: A multiplexer selects one input using a binary control value. Input count determines the required number of selector bits for a power-of-two design. Governing rule: A 2ᵏ-to-1 multiplexer uses k selector bits.

Question 3: transfer to lexical analysis and tokens

Does tokenisation alone prove the entire programme is syntactically and semantically valid?

Answer: No. Parsing and semantic checks are separate stages.

This is an interleaved related-skill task, not a claim that the two topics have identical methods. Explain which idea changes when switching from the main topic to this one.

Review the attempt

Separate correct answers reached with a justified method from lucky guesses. Rework missed steps without looking at the answer, then use a fresh problem from an appropriate primary textbook or official paper. Do not use a small worksheet result as an admission cutoff, rank or readiness guarantee.

Official sources and verification

Sources checked on 26 October 2026. A source’s date, programme and campus limit which claims it supports. Official pages may change after review.

1. UEM Kolkata — IEMCET 2026 syllabus and instructions

   Historical course-specific preparation guidance. Some introductory route text conflicts with the central portal.

2. WBJEEB — JECA 2026 information bulletin

   2026 MCA syllabus and institution modules; Appendix 10 includes IEM Salt Lake. Historical, not a 2027 seat guarantee.

3. IIT Madras — GATE 2027 Computer Science syllabus

   Current GATE CS topic reference; IEMCET adoption of every 2027 revision is not asserted. MCA eligibility and programme paper instructions remain separate.

Found a discrepancy? Send the page and the official notice for correction.