第5章 算术运算指令.ppt

CHAPTER 5 Arithmetic and Logic Instructions(算术和逻辑运算指令)(P. 147) 5-1 ADDITION, SUBTRACTION, AND COMPARISON (P. 147) Most arithmetic and logic instructions only change the flags located in the rightmost eight bits of the flag register (sign, zero, carry, auxiliary carry, and parity) and overflow flag. The other flags do not change. Overflows occurs when signed numbers are added or subtracted. O=Cs⊕Cp. 5-1 Addition (加法指令)(P. 148) Addition-without-Carry Increment Addition Addition-with-Carry Addition-without-Carry(不带进位的加法指令)(P. 148) Format: ADD DESTINATION,SOURCE Operation: DESTINATION←DESTINATION＋SOURCE NOTES: The destination and source are both byte- or word-sized data. The only types of addition not allowed are memory-to-memory and segment register additions. Forms: ADD AL,BL ADD BX,245FH ADD [BX+DI],DL EXAMPLE 5-2 MOV DL, 12H ADD DL, 33H EXAMPLE MOV AL, 7CH ADD AL, 38H Increment Addition(加1指令)(P. 151) Increment addition adds 1 to a register except the segment registers or a memory location. Format： INC DESTINATION Operation： DESTINATION←DESTINATION＋1 Notes: The increment instructions do not affect the carry flag bit. With indirect memory increments, the size of the data must be described by using the BYTE PTR, WORD PTR, or DWORD PTR directives. Forms： INC BL INC SP INC WORD PTR[BX] Addition-with-Carry(带进位的加法指令)(P.152) An addition-with-carry instruction (ADC) adds the bit in the carry flag to the operand data. This instruction mainly appears in software that adds numbers that are wider than 16-bits in the 8086-80286. Format ADC DESTINATION,SOURCE Operation DESTINATION ←DESTINATION＋SOURCE＋C NOTES: The destination and source are both byte- or word-sized data. Forms ADC AL,AH ADC BX,[BP+2] EXAMPLE 5-7 ;A procedure that sums BX-AX and DX-CX; ;the result is returned in BX-AX SUM32 PROC NEAR ADD AX,CX ADC BX,DX RET SUM32 ENDP 5-1-2 Subtraction (减法指令)(P. 153) Subtraction-without-Borrow Decrement Subtraction Subtraction-with-Borrow Subt