MOVS/MOVSB/MOVSW/MOVSD/MOVSQ — Move Data from String to String. . Opcode, Instruction, Op/En, 64-Bit Mode, Compat/Leg Mode, Description. A4 The MOV instruction copies the value of Operand2 into Rd . In certain circumstances, the assembler can substitute MVN for MOV , or MOV for MVN . The MOV instruction moves data bytes between the two specified operands. The byte specified by the second operand is copied to the location specified by the MOVS - Move String (Byte or Word) Usage: MOVS dest,src MOVSB MOVSW MOVSD (386+) Modifies flags: None Copies data from addressed by DS:SI (even if operandsMOVS/MOVSB/MOVSW/MOVSD--Move Data from String to String​​ The address of the destination operand is read from the ES:EDI or the ES:DI registers (again depending Load the correct index values into (E)SI and (E)DI before executing the MOVS instruction. MOVSB, MOVSW, and MOVSD are synonyms for the byte, word, and The MOVSB instruction tells the assembler to move data as bytes; the MOVSW implies the string is to be moved as words. Usage MOVS dest, src (This usage is