Question

The first program is to count the number of zeros in $3855. Please

    add comments to each line

         

      org   $1000

array     db $38, $55 ; data to be tested

          

          org $1100

zero_cnt ds.b   1

lp_cnt     ds.b   1

             org   $1500

             clr   zero_cnt       ;initialize the 0 count to 0

             movb #16,lp_cnt     

             ldd   array        

again     lsrd

            bcs   chk_end         ;

            inc   zero_cnt

chk_end   dec   lp_cnt              

            bne   again                  

            swi             

            end

Answer 1

org   $1000 #  set the location counter to $1000

array     db $38, $55 # data to be tested

initializes 2 bytes in memory to 
$38
$55

and the assembler will use array as the symbolic address of the first byte whose initial value is 
$38. The program can also force these 2 bytes to a certain address by adding the org directive. 
For example, the sequence

org $1000 

db $38,$55 


array 

          

   org $1100 #  set the location counter to $1100

zero_cnt ds.b   1 # variable to store the number of zeroes

lp_cnt     ds.b   1 # variable for the loop counter

             org   $1500 # set the location counter to $1500

             clr   zero_cnt # initialize the 0 count to 0

             movb #16,lp_cnt    # initialize lp_cnt  to 16

             ldd   array #place 16 bit number in D

again     lsrd #shift the lsb of D to the C flag

            bcs   chk_end #branch if the C flag (= LSB bits) is 1

            inc   zero_cnt #increment 0s count if the lsb is a 0

chk_end   dec   lp_cnt #check to see if D is already 0

            bne   again #check to see if we tested all   

            swi             

            end