F = (A + B)·(B + C) — SOP and POS

corePOS in, both canonical forms out

Answer

Σm(2,3,5,6,7) = ΠM(0,1,4)

Why this example is worth doing

Entered as a product of sums rather than a sum of products, because half of all problem sets on this topic start from POS and most tools quietly assume SOP. Each factor is missing a variable and expands by adding X·X̄ — the dual of the SOP expansion step, and the one textbooks explain in half a sentence. The page shows both expansions side by side so the symmetry is visible rather than asserted.

Try your own input in the SOP & POS canonical forms. Expand to canonical minterms and maxterms, and convert between the two.

How the answer is reached

Canonical sum of products

A′ · B · C′ + A′ · B · C + A · B′ · C + A · B · C′ + A · B · C

Canonical product of sums

(A + B + C) · (A + B + C′) · (A′ + B + C)

Truth table

Truth table — columns #, A, B, C, F
#ABCF
00000
10010
20101
30111
41000
51011
61101
71111

Compare with

Open this example in the SOP & POS canonical forms

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

  • Shannon, “A Symbolic Analysis of Relay and Switching Circuits” (1938)
  • McCluskey, “Minimization of Boolean Functions” (1956)