Bitwise logical operations
	R-type
		and $rd, $rs, $rt  # R[d] <- R[s] & R[t]								Bitwise AND
		or  $rd, $rs, $rt  # R[d] <- R[s] | R[t]								Bitwise OR
		nor $rd, $rs, $rt  # R[d] <- ~(R[s] | R[t])								Bitwise NOR
		xor $rd, $rs, $rt  # R[d] <- R[s] ^ R[t]								Bitwise XOR
		what about bitwise negation (complement)?
			can use XOR with -1:
			addi    $8,$0,0x42   # put 2's comp. hex 42 into register 8
				what value is in register 0?
			addi    $9,$0,-1     # put 2's comp. -1 into register 9
				note sign bit extension for immediate value
			xor     $10,$8,$9    # xor register 8 and 9, result in 10
			$r8	0000	0000	0000	0000	0000	0000	0100	0010	42
			$r9	1111	1111	1111	1111	1111	1111	1111	1111	-1
			$r10	1111	1111	1111	1111	1111	1111	1011	1101
			example of fewer instruction types --> more instructions
		also no NAND (negated AND)