# Hexadecimal arithmetic on calculator (casio etc.)

When I do hexadecimal subtraction say, 2A-324 on a casio calculator or any calculator in general, i get the result as FFFFFD06

Why do i get so many F's ?? dosnt F stand for 15 in hex. In any general arithmetic, how many digits should i consider for the final answer, say in a subtraction operation in which the bigger number is negetive (324 in my example).

You get this result because the calculator uses only 32 bit arithmetic in this case, i.e. it actually computes $\mod 2^{32}.$ $$2A_{16}-324_{16}= -2FA_{16}$$ $$2A_{16}-324_{16}+ 2^{32}= FFFFFD06_{16}$$