‘mystring + 1’ is the address of the second byte of the string.
mov al, mystring + 1
stores (the least significant byte of) that address in al. To indicate that you don’t want to store the address but the byte located at that address, write this:
mov al, [mystring + 1]
To declare a four-bytes integer equal to say, 42, use:
myint dd 42
4
solved NASM – Variable Basics