The sum of minterms representation of a Boolean function is formed by OR-ing

• A. The minterms for all input combinations that yield output 1
• B. All possible minterms regardless of output
• C. The minterms for which the output is 0
• D. The maxterms of the function

Answer: (A)

Minterms are product terms that are true for exactly one input combination. In the sum of minterms form, you take the minterms corresponding to every input pattern for which the Boolean function outputs 1 and OR them together. Each chosen minterm ensures the function is 1 only for its specific input pattern, and OR-ing all of them makes the function evaluate to 1 for all the input patterns where the function should be 1, while keeping it 0 for all patterns where it should be 0. Including minterms for input patterns that yield 0 would force the function to be 1 there as well, which isn’t correct. The maxterms, by contrast, relate to a canonical product of sums representation, not the sum of minterms. Hence, the sum of minterms is formed by OR-ing the minterms for all input combinations that yield output 1.