Digital Logic Toolkit

Digital Logic Toolkit — OR gate

Source
https://digitallogictoolkit.com/or-gate/
Printed

Full 2-input truth table — OR gate

intro3 of 4 rows true

Answer

output column 0111

Why this example is worth doing

Three rows in four are true, making OR the permissive counterpart to AND's selectivity. The page reads the table the other way round as a technique: it is quicker to describe OR by its single false row — both inputs low — than by its three true ones, and that habit of characterising a function by whichever set is smaller is what the OFF-set minimisation method on the K-map page formalises. Same idea, introduced here on four rows.

Try your own input in the OR gate. Truth table, symbol and algebraic form for A + B, with a live two-input toggle.

How the answer is reached

Truth table

Truth table — columns #, A, B, A + B
#ABA + B
0000
1011
2101
3111

Compare with

Open the OR gate

This input is entered in the tool itself — it is too rich for a link to carry.

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.
  • Gate symbols follow whichever standard the header toggle is set to: ANSI/IEEE Std 91-1984 distinctive shapes, or IEC 60617-12 rectangles.

Sources

  • ANSI/IEEE Std 91-1984, Graphic Symbols for Logic Functions
  • IEC 60617-12, Graphical Symbols for Diagrams — Binary Logic Elements