A·B + Ā·C + B·C — Boolean simplification

coreconsensus; the B·C term is redundant

Answer

A′ · C + A · B

Why this example is worth doing

The consensus theorem. B·C is the consensus term of A·B and Ā·C — it contains the literals left over when A and Ā cancel — and it is covered by the other two, so it can be deleted without changing a single row. This matters commercially, not just algebraically: deleting it removes an AND gate and two wires from the synthesised circuit. It is also the classic hazard-removal term, so the page notes that in a real gate-level design you sometimes deliberately keep the redundant term back.

Try your own input in the Boolean algebra simplifier. Simplify any expression to its minimal SOP and POS, one named law at a time.

How the answer is reached

Step by step

A · B + A′ · C + B · CA · B + A′ · CConsensus — A · B + A′ · C + B · C = A · B + A′ · C

Warning:

A · B + A′ · C + B · C simplifies to A · B + A′ · C in 1 step. That is a proven minimum (2 terms, 4 literals), not a best effort. It is the only minimum-cost form.

Quine–McCluskey

Prime implicants — Quine–McCluskey
#Term
1A′ · C
2B · C
3A · B
Minimum cover — Quine–McCluskey
#Cover
1A′ · C + A · B
Warning:

2 term(s), 4 literal(s); 2 essential prime implicant(s).

Truth table

Truth table — columns #, A, B, C, F
#ABCF
00000
10011
20100
30111
41000
51010
61101
71111

Compare with

Open this example in the Boolean algebra simplifier

The field arrives filled in with this example’s input.

Note:

Notation this page assumes

  • Symbols: · is AND, + is OR, ⊕ is XOR, a prime or an overline is NOT. The field also takes ∧ ∨ ¬ ~ ! & | and the words.
  • Operator precedence, tightest first: NOT, then AND (including juxtaposition), then XOR/XNOR, then NAND/NOR, then OR, then IMPLIES, then IFF.
  • In a minterm index the first variable is the most significant bit, so over [A, B, C] minterm 5 is A·B̄·C.

Sources

  • Boole, An Investigation of the Laws of Thought (1854)
  • Shannon, “A Symbolic Analysis of Relay and Switching Circuits” (1938)