The Texas Instruments TI-1025 calculator could add, subtract, multiply, and divide. It even could hold a number in memory, thanks to its 9-volt battery. I saved up and paid $9.99 for this at Pay n Save in 1977 in preparation for a math class.

For some reason I still have it.

The display is made of LED numbers. One recently sold on eBay for $15. If I ever find a 9-volt around my house I’m going to try it out.