Logical Design of n-bit Comparators: Pedagogical Insight from Eight-Variable Karnaugh Maps

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Ali Muhammad Ali Rushdi
Sultan Sameer Zagzoog


An -bit comparator is a celebrated combinational circuit that compares two -bit inputs  and  and produces three orthonormal outputs: G (indicating that  is strictly greater than ), E (indicating that  and  are equal or equivalent), and L (indicating that  is strictly less than ). The symbols ‘G’, ‘E’, and ‘L’ are deliberately chosen to convey the notions of ‘Greater than,’ ‘Equal to,’ and ‘Less than,’ respectively. This paper analyzes an -bit comparator in the general case of arbitrary  and visualizes the analysis for  on a regular and modular version of the 8-variable Karnaugh-map. The cases  3, 2, and 1 appear as special cases on 6-variable, 4-variable, and 2-variable submaps of the original map. The analysis is a tutorial exposition of many important concepts in switching theory including those of implicants, prime implicants, essential prime implicants, minimal sum, complete sum and disjoint sum of products (or probability-ready expressions).

Comparator, Karnaugh map, prime implicant, minimal sum, complete sum, probability-ready expression.

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How to Cite
Rushdi, A., & Zagzoog, S. (2019). Logical Design of n-bit Comparators: Pedagogical Insight from Eight-Variable Karnaugh Maps. Journal of Advances in Mathematics and Computer Science, 32(3), 1-20. https://doi.org/10.9734/jamcs/2019/v32i330146
Original Research Article


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