Assembly Language StepbyStep Programming with DOS and Linux 2nd Ed [Electronic resources] نسخه متنی

OR Logical OR

Flags affected:

O D I T S Z A P C  OF: Overflow flag  TF: Trap flag AF: Aux carry
F F F F F F F F F  DF: Direction flag SF: Sign flag PF: Parity flag
*       * * * * *  IF: Interrupt flag ZF: Zero flag CF: Carry flag

Legal forms:

OR r8,r8
OR m8,r8
OR r8,m8
OR r16,r16
OR m16,r16
OR r16,m16
OR r32,r32    386+
OR m32,r32    386+
OR r32,m32    386+
OR r8,i8
OR m8,i8
OR r16,i16
OR m16,i16
OR r32,i32    386+
OR m32,i32    386+
OR AL,i8
OR AX,i16
OR EAX,i32    386+

Examples:

OR EBX,EDI
OR AX,0FFFFH            ;Uses single-byte opcode
OR AL,42H               ;Uses single-byte opcode
OR WORD [ES:BX],0B800H
OR WORD [BP+SI],DX

Notes:

OR performs the OR logical operation between its two operands. Once the operation is complete, the result replaces the destination operand. OR is performed on a bit-by-bit basis, such that bit 0 of the source is ORed with bit 0 of the destination, bit 1 of the source is ORed with bit 1 of the destination, and so on. The OR operation yields a 1 if one of the operands is 1; and a 0 only if both operands are 0. Note that the operation makes the Auxiliary carry flag undefined. CF and OF are cleared to 0, and the other affected flags are set according to the operation's results.

r8 = AL AH BL BH CL CH DL DH        r16 = AX BX CX DX BP SP SI DI
sr = CS DS SS ES FS GS              r32 = EAX EBX ECX EDX EBP ESP ESI EDI
m8 = 8-bit memory data              m16 = 16-bit memory data
m32 = 32-bit memory data            i8 = 8-bit immediate data
i16 = 16-bit immediate data         i32 = 32-bit immediate data
d8 = 8-bit signed displacement      d16 = 16-bit signed displacement
d32 = 32-bit unsigned displacement