vhdl code for RAM memory

I have a question...what is the meaning of the two ** in the following piece of code: TYPE RAM IS ARRAY(0 TO 2 ** ADDRESS_WIDTH - 1) OF std_logic_vector(DATA_WIDTH - 1 DOWNTO 0);

Solution

It's being used to indicate exponentiation / raising x to the power of y. The ^ symbol commonly used for exponentiation in written math is used for the exclusive-or (XOR) operation in many languages, so the ones that also support exponentiation use a different symbol.

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