8088/8086 Instruction I

Direction Flag Direction Flag (DF) is used to control the way SI and DI are adjusted during theexecution of a string instruction— DF=0, SI and DI will auto-increment during the execution; otherwise, SI and DIauto-decrement— Instruction to set DF: STD; Instruction to clear DF: CLD— Example:CLDMOV CX, 5REP MOVSBAt the beginning of execution,DS=0510H and SI=0000HDS : SI0510:00000510:00010510:00020510:00030510:00040510:00050510:000653484F50504552SHOPPERSI CX=5SI CX=4SI CX=3SI CX=2SI CX=1SI CX=0Source String8-14