Adding machine and Personal digital assistant

Adding machine noun - A calculator that performs simple arithmetic functions.

Personal digital assistant and adding machine are semantically related. In some cases you can use "Personal digital assistant" instead a noun phrase "Adding machine".

Personal digital assistant noun - A lightweight consumer electronic device that looks like a hand-held computer but instead performs specific tasks; can serve as a diary or a personal database or a telephone or an alarm clock etc..

Adding machine and personal digital assistant are semantically related. You can use "Adding machine" instead a noun phrase "Personal digital assistant".