Which instruction would you use to check if one or both bits in two different words are logic '1'?

To determine if one or both bits in two different words are logic '1', the most suitable instruction is the OR instruction. The OR operation performs a logical disjunction: it evaluates two binary inputs and returns '1' if either of the inputs is '1'. Thus, if at least one of the bits in the two words is '1', the result will be '1', fulfilling the requirement of checking for the presence of logic '1' in either word.

For instance, if you have two sets of bits in different words, the OR instruction will yield a '1' if either word has a '1' in the respective bit position. This makes it particularly effective for checking the condition stated in the question.

On the other hand, while the AND instruction would require both bits to be '1' to return a '1', it does not satisfy the requirement of finding at least one '1'. The NOR and XOR instructions also do not fit the need; NOR would only return '1' if both bits are '0', and XOR only indicates whether the bits differ rather than checking for presence of '1'. Therefore, the OR instruction stands out as the most appropriate choice for the task at hand.