title: What does a identity element mean in boolean algebra?
body: <p>I'm reading The Art of Assembly Programming by Randa Hyde (<a href="http://www.ic.unicamp.br/~pannain/mc404/aulas/pdfs/Art%20Of%20Intel%20x86%20Assembly.pdf" rel="nofollow">http://www.ic.unicamp.br/~pannain/mc404/aulas/pdfs/Art%20Of%20Intel%20x86%20Assembly.pdf</a>) and I've reached the following statement in the book: "P4 The identity element with respect to • is one and + is zero. There is no identity
  element with respect to logical NOT." but I don't entirely understand what its saying. Can someone help me understand this sentence? English is my first language and I can normally read anything, but this is a bit confusing. I also know normal algebra, so most of this isn't new to me. I know what the additive and multiplicative identities are in plain ole' algebra.</p>