Is calculator allowed in ___ ?

Is calculator allowed in GATE exam? Is calculator allowed in GRE? Or is calculator allowed in Tech Mahindra Aptitude Test? - some of the questions we get almost every week through email! I thought we'd have a discussion where we discuss which exams allow the use of scientific calculator and which exams don't.

I know for sure:-

1. Calculator is NOT allowed in GRE
2. Calculator is NOT allowed in Tech Mahindra Aptitude Test, or any aptitude test I know.

3. GATE, I believe has an option of on-screen scientific calculator. Someone needs to confirm this though.

Looking forward to responses from fellow engineers.

This announcement from IITK clears the doubt:
Question 06:
Can I use a calculator during the examination?
Answer:
Yes. You can use your own non-programmable calculator.

IIT GATE 2015

Thanks! It looks like the system has changed in the recent times. Here's the latest FAQ snippet from GATE 2017 page: FAQGATE 2017 | IITRGATE2017

Can I use a physical calculator during the examination?
NO. During the online GATE 2017 examination, all candidates will be provided with a virtual scientific calculator which has to be used to answer the questions. No physical calculator will be allowed inside the examination hall. The same applies to mobile phones and wrist watches with calculation facility. GATE 2017 will not provide any storage space at examination locations for such objects. If a candidate brings personal belongings including mobile phones, those will have to be kept outside the examination hall at the candidate’s risk. If the candidate is found to be in possession (even if not using) of any calculator and mobile phone and wrist watch with calculation facility, he/she shall be disqualified and the result shall not be declared for the candidate.

Till 2016, it was allowed to use physical scientific calculator.