What is the name of the Boolean function whose output is always one?

73 Views Asked by Bumbble Comm At 18 Apr 2026 - 6:05

For example:

f = a.b.c.d + !a.!b.!c.!d + a.!d + !a.b.!c + !b.d + b.c.d  + a.b.!c.d
+ !a.c.!d = 1

! is logical NOT, . is logiacal AND and + is logical OR.

The function has a special name. What is the name of that function? Thanks.

There are 2 best solutions below

Bumbble Comm On 18 May 2015 - 5:21 BEST ANSWER

It is called a tautology. You may look at the wikipedia page http://en.wikipedia.org/wiki/Tautology_%28logic%29

Bumbble Comm On 18 May 2015 - 5:19

It's usually called $1$.

If you call your truth values something else, then the name changes accordingly.