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

coretwo 2-literal terms

Answer

A′ · C + B · C

Why this example is worth doing

Three minterms that share a common literal C, which is the cue to factor before doing anything else: C·(Ā·B̄ + Ā·B + A·B). Inside the bracket the first two terms combine to Ā and the second and third to B, and note that the middle minterm has been used twice. That is legal — idempotence lets you write X = X + X — and it is the algebraic counterpart of overlapping two circles on a K-map. Students who believe each minterm belongs to exactly one group get stuck here.

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′ · C + A′ · B · C + A · B · CA′ · C · (B′ + B) + A · B · CFactoring (distributive, right to left) — A · B + A · C = A · (B + C)

A′ · C · (B′ + B) + A · B · CA′ · C · 1 + A · B · CComplement — A + A' = 1

A′ · C · 1 + A · B · CA′ · C + A · B · CIdentity — A · 1 = A

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

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

Warning:

A′ · B′ · C + A′ · B · C + A · B · C simplifies to A′ · C + B · C in 5 steps. 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
Minimum cover — Quine–McCluskey
#Cover
1A′ · C + B · C
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
61100
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)