boolean-logicdemorgans-law

Name of axiom that tells you that (A OR B) is NOT(NOT A AND NOT B)

I'm having a mental block here.

What is the name of the axiom / theorem that tells you that

(A OR B) == NOT(NOT A AND NOT B)

I'm about to review some C code and can't remember that this is called.

Solution

  • It is the De Morgan's law. It's usually expressed as

    "not (A and B)" is the same as "(not A) or (not B)"

    or

    "not (A or B)" is the same as "(not A) and (not B)"