Search code examples
booleanlogicboolean-logicboolean-expressionboolean-operations

Why are products called minterms and sums called maxterms?

Do they have a reason for doing so? I mean, in the sum of minterms, you look for the terms with the output 1; I don't get why they call it "minterms." Why not maxterms because 1 is well bigger than 0?

Is there a reason behind this that I don't know? Or should I just accept it without asking why?

Solution

  • The convention for calling these terms "minterms" and "maxterms" does not correspond to 1 being greater than 0. I think the best way to answer is with an example:

    Say that you have a circuit and it is described by X̄YZ̄ + XȲZ.

    "This form is composed of two groups of three. Each group of three is a 'minterm'. What the expression minterm is intended to imply it that each of the groups of three in the expression takes on a value of 1 only for one of the eight possible combinations of X, Y and Z and their inverses." http://www.facstaff.bucknell.edu/mastascu/elessonshtml/Logic/Logic2.html

    So what the "min" refers to is the fact that these terms are the "minimal" terms you need in order to build a certain function. If you would like more information, the example above is explained in more context in the link provided.

    Edit: The "reason they used MIN for ANDs, and MAX for ORs" is that:

    In Sum of Products (what you call ANDs) only one of the minterms must be true for the expression to be true. In Product of Sums (what you call ORs) all the maxterms must be true for the expression to be true.