tailieunhanh - The 80x86 IBM PC and Compatible Computers- P19

The 80x86 IBM PC and Compatible Computers- P19: Praised by experts for its clarity and topical breadth, this visually appealing, one-stop source on PCs uses an easy-to-understand, step-by-step approach to teaching the fundamentals of 80x86 assembly language programming and PC architecture. Offering users a fun, hands-on learning experience, it uses the Debug utility to show what action the instruction performs, then provides a sample program to show its application. | LOOPNE LOOPNZ LOOP While CF Not Zero and ZF Equal Zero Flags Unchanged- Format LOOPxx target DEC CX then jump if CX and ZF not zero Function Decrements CX by 1 then jumps to location indicated by the operand if CX and ZF are not zero otherwise continues with the next instruction below the LOOP. In other words it will exit the loop if CX becomes 0 or ZF 1. Example Assume that the daily temperatures for the last 30 days have been stored starting at memory location with offset 1200H. LOOPE can be used to find the first day that had a 90-degrce temperature. MOV SET UP THE COUNTER MOV SETUP THE POINTER AGAIN CMP DI 90 INC DI LOOPNE AGAIN MOV Move Flags Unchanged. Format MOV dest source copy source to dest Function Copies a word or byte from a register memory location or immediate number to a register or memory location. Source and destination must be of the same size and cannot both be memory locations. MOVS MOVSB MOVSW Move Byte or Word String Flags Unchanged. Format MOVSx Function Moves byte or word from memory location pointed to by DS SI to memory location pointed to by ES DI. If DF 0 both pointers are incremented otherwise they are decremented. SI and DI are incremented decremcnted by 1 or 2 depending on whether it is a byte or word string. When used with the REP prefix CX is decremented each time until CX is zero. MUL Unsigned Multiplication Flags Affected OF CF. Unpredictable SF ZF AF PF. Format MUL source AX source x AL or DX AX source x AX Function Multiplies an unsigned byte or word indicated by the operand by a unsigned byte or word in AL or AX with the result placed in AX or DX AX. NEG Negate Flags Affected OF SF ZF AF PF CF. Format NEG dest negates operand Function Performs 2 s complement of operand. Effectively reverses the sign bit of the operand. This instruction should only be used on signed numbers. NOP No Operation Flags Unchanged. Format NOP Function Performs no operation. Sometimes used for timing delays to waste clock cycles. Updates