Digital Logic Toolkit

Digital Logic Toolkit — OR gate

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

A = 1, B = 0 — OR gate

introinclusive, not exclusive

Answer

output 1

Why this example is worth doing

One input high and the output is high — the row that separates OR from XOR and from the English word "or". Ordinary speech usually means exclusive or ("tea or coffee"), while the gate is inclusive: it is also true when both inputs are true. That mismatch is the single most common source of specification errors when students translate a word problem into logic, so the page puts the two output columns adjacent and highlights the one row where they differ.

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

The probed row

A = 1, B = 01— Row 2 of 4.

Truth table

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

Compare with

Open this example in the OR gate

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.
  • 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