Note that NOT operation, being the unary one, can be obtained by the specific case of combined NOR instruction (C5 operation code): X = NOT(X OR 0)

Code	Mnemonic	Name	Comments
C0	OR $X, $Y, $Z	bitwise OR	each bit of register Y is logically "ored" with register Z; the result is stored into register X
C1	OR $X, $Y, Z	bitwise OR	each bit of register Y is logically "ored" with the constant Z; the result is stored into register X
...
C5	NOR $X, $Y, Z	bitwise OR-NOT	NOR $X, $X, 0 is equivalent to NOT X$!
C6	XOR $X, $Y, $Z	bitwise XOR	each bit of register Y is logically "xored" with register Z; the result is stored into register X
C7	XOR $X, $Y, Z	bitwise XOR	each bit of register Y is logically "xored" with the constant Z; the result is stored into register X
C8	AND $X, $Y, $Z	bitwise AND	each bit of register Y is logically "anded" with register Z; the result is stored into register X
C9	AND $X, $Y, Z	bitwise AND	each bit of register Y is logically "anded" with the constant Z; the result is stored into register X

Examples:

• instruction OR $1, $6, $7 executes logical operation OR with registers 6 and 7 and places the result to register 1
• instruction OR $1, $6, 7 executes logical operation OR with registers 6 and constant 7, i.e. sets 3 lowest bits in its value, and stores the result to register 1
• instruction NOR $3, $3, 0 calculates binary complement of registers 3

"MMIX basics" page