汇编:DF标志位
DF: ? ?UP(向上) ? DN(down 向下)
assume cs:code, ds:data, ss:stackdata segmentdb 128 dup(128) data endsstack segmentdb 128 dup(128) stack endscode segmentstart: mov dx, stackmov ss, dxmov sp, 128call cpy_Bootmov ax, 4C00Hint 21H Boot: mov ax, 1000Hmov ax, 1000Hmov ax, 1000Hmov ax, 1000H Boot_end: nop;======================================= cpy_Boot:mov bx, csmov ds, bx ; ds:[si]mov si, OFFSET Bootmov bx, 0mov es, bxmov di, 7E00H ; es:[di]mov cx, OFFSET Boot_end - Bootcld ; inc si, inc di DF=0; movsb 復(fù)制一個(gè)字節(jié)從ds:[si] 到 es:[di]rep movsb ;rep 重復(fù) movsb:復(fù)制字節(jié);rep movsw 移動(dòng)一個(gè)字型數(shù)據(jù),同時(shí)每次si,di都會(huì)再加2retcode endsend start?
總結(jié)