I was about eight when my oldest brother got a 'pocket' calculator. It was pale brownish-grey, and the numbers showed up in red. It did the four basic rules of arithmetic - add, subtract, multiply, divide and we were all very impressed by it.
Of course, the thrill of doing arithmetic soon wore off, but then we discovered that if you turned the calculator upside down, some numbers looked like letters, and you could spell words - there was one trick where you told a story about a woman taking various numbers of pills - typing in the numbers as you told it - and the final effect of the pills was revealed when you turned the calculator upside down and revealed that by taking "55378008" pills, she would end up "BOOBLESS". Absolutely shocking to an eight year old in 1974!