<DEFINT A-Z
CLS
A$ = "f"
A = ASC(A$)
N = A ^ 4 - 600 * 23
PRINT N
END>

If I put DEFLNG instead of DEFINT, N returns a different value. Why?

DEFLNG defines "longs" while DEFINT defines "integers". Integers in QB64 are 2-bytes meaning that they can store the values between -32768 and 32767. Longs are 4-bytes and store -2147483648 to 2147483647.

Your expression "A ^ 4" computes to roughly 108243216, which causes an overflow if A is an integer. If it's a long, it will evaluate to its correct value.

Hope this helps!