mov ( $1234_5678, ebx ); copies the hexadecimal value 0x1234_5678 into the ebx register.

stdout.put ( ebx ); would print that hexadecimal value.

stdout.put ( [ebx] ); would print the 32-bit value that is stored at the memory location 0x1234_5678.

Caveats about whether or not accessing data at that memory address is allowed.