Can I carry my computer as a carry-on on a international flight?

AFAIK, the recent ban only covered flights to the US and has just been lifted as far as Royal Jordanian is concerned so you should be fine. A ban is still in place for flights to the UK from Queen Alia Airport.

In general, laptops are allowed on international flights so it should be perfectly fine on other flights.

The rules apply to any electronics and carry on. It must fit within the size limit and be within the weight limit too (if any, check with the airline but if you fly Delta there is none on most flights).

The potential difficulty when travelling with a standard computer as opposed to a laptop is that one is supposed to be able to show that it is working. Since you cannot carry a UPS with you, it being a giant battery, you will have to plug it in at security if requested, so be sure to have electric plug adapters and a voltage-switching power-supply, if you are goingthrough a place with different electrical standard.

Note that sometimes you are requested to gate-check a bag even though it fits within the official limit, so make sure it is packed suitably to be handled by anyone just in case. If your computer uses HDDs with moving platters, take them out and carry them personally since they are the most fragile. Even if asked to power the computer on, it will no longer boot but still show some output.

It is a good idea to have a proof-of-purchase for the return since customs in your home country may want to verify that you are not importing new electronics. In some countries, you have to declare items above a certain value when going in, so the receipt can be useful there. Still, be prepared to justify this more than once. Just two weeks ago, I was flying with a computer and was asked by customs and by security what it was and why I had to bring my own.