Program to check whether a 4th bit of a byte is 1, Store FFh if 1, else store 00 in the same location in 8051

mov dptr,#9000h

movx a,@dptr ;move data from external memory location to a

jnb 0e3h,down ;jump to location down, if 4^th bit of a is set

inc dptr ;increment dptr

mov a,#0ffh ;move 0ffh to a

movx @dptr,a ;move data from a to external memory location

sjmp last ;jump to location last

down:mov a,#0h ;move 00 to a

inc dptr ;increment dptr

movx @dptr,a ; move data from a to external memory location

last:sjmp last

end