I know if it's \$ \Sigma \$ we put 1's in the Karnaugh map, but I don't know what \$ d \$ is.

$$ f(a,b,c,d) = \Sigma m(0,1,4,10,15) + d(7,14) $$

From what I've googled, https://en.wikipedia.org/wiki/Karnaugh_map it seems to be a "don't care", but I'm not so sure, because this is the first time I've seen this, and on the link and no where else can I see a \$ d() \$ reference.

  • 2
    \$\begingroup\$ You are correct. It is Don't Care! Kind of strange since d is also an input. \$\endgroup\$ May 19 at 16:51
  • \$\begingroup\$ I should use X in place of d. m is abbreviation for "minterm" ... \$\endgroup\$
    – Antonio51
    May 19 at 16:53

1 Answer 1


Here is an example of d(...) being used for don't care conditions marked with an X: -

enter image description here

Image from Quora. Here's another example: -

enter image description here

Image from here.


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