One unexpected advantage in some circumstances of a slide rule over current portable computing devices is that it does not have memory.
You are allowed to bring a calculator to ham radio license exams in the US, but you have to clear its memory (both data and program memory for programmable calculators) first. If the examiners aren't sure you have done so, they are supposed to disallow the calculator.
Unlike many other standardized tests, there is no specific list of what calculators are allowed. I brought my HP-15C, but wasn't sure that the examiners would be familiar with it and so wasn't sure I'd be able to convince them that I had cleared it.
I also brought a slide rule. That way if the examiners disallowed my HP-15C I'd still be covered.
They did allow the HP-15C, and it turned out that even though I took all three exams (Technician, General, and Extra) that day, I only actually used the calculator once. The questions are all multiple choice, and there was only one where a quick mental approximation wasn't enough to identify the right answer.
Nitpick: a slide rule does have memory, but it is small and gets cleared when doing computations. One typically can store one number by moving the slide and another one by location of the cursor.
It also is fairly hard to hide the fact that the memory isn’t cleared.
Many slide rules also have some read-only memory, for example ’storing’ the constant π.
You are allowed to bring a calculator to ham radio license exams in the US, but you have to clear its memory (both data and program memory for programmable calculators) first. If the examiners aren't sure you have done so, they are supposed to disallow the calculator.
Unlike many other standardized tests, there is no specific list of what calculators are allowed. I brought my HP-15C, but wasn't sure that the examiners would be familiar with it and so wasn't sure I'd be able to convince them that I had cleared it.
I also brought a slide rule. That way if the examiners disallowed my HP-15C I'd still be covered.
They did allow the HP-15C, and it turned out that even though I took all three exams (Technician, General, and Extra) that day, I only actually used the calculator once. The questions are all multiple choice, and there was only one where a quick mental approximation wasn't enough to identify the right answer.