Count number of negative numbers in array

Program Description

Counts the number of negative number in the array stored in the memory in data segement. Assumes the numbers stored in HEX format.Outputs the count in HEX format

Program
;************************************************
;   code.cheraus.com
;
;# Algorithm:    ANDs the given number with 80H:
;                If the result is zero     -> number is positive
;                If the result is non-zero -> number is negative

;   The number should be stored in the correct format
;;   80H -negative (as 128 in decimal.Since max limit for signed number in
;                  8 bit format is 127, 128 is negative)
;   However if simply 80 is stored, it is non negative
;
;************************************************

;macro to print the number

print macro m
mov ah,09h
mov dx,offset m
int 21h
endm



.model small

.data

list db 10,20,80h,86h,23,26,12,57,89h  ;array of numbers
count db (0)                           ;count variable(to store answer) 

msg db 10,13, "The number of negative numbers is: $"  ;output message

.code

start:  mov ax,@data
        mov ds,ax

        mov ch,00                 ; temp storage of ans
        mov si,offset list        ;point to start of array
        mov cl,09                 ;count of numbers in the array

again:  mov al,[si]               ;copy num in al
        and al,80h                ;AND with 80H
        jz next                   ; jump to next statement if result is zero
                                  ; i.e. positive number. Else increase count

        inc ch                    ;increment count if negative number if ANDing
                                  ; gives non zero value 


next:

        inc si                   ;inc si to point to next location in array
        dec cl                   ;decrement count of the array to check
        jnz again                ;if all numbers aare not covered do again


        mov bl,ch                ;store the answer in bl



     ;printing the result

        print msg              ;print the string

        mov cl,04              ;count for shifting to display a number
        mov al,bl              ;copy ans in "AL" register

        and al,0f0h            ;Mask the LSB and take only MSB
        shr al,cl              ;shift the numberto bring MSB to LSB

        cmp al,09              ;if it is number 0-9 just add 30H
        jbe alpha              ; if character A-F add additional 7
        add al,07              ; for correct ASCII value to display


alpha:  add al,30h             ; add 30H to make the number ASCII
        mov ah,02              ; display function
        mov dl,al              ; content to be displyed needs to be in DL
                               ;  for 02 function
        int 21h


       ;printing LSB digit

        mov ah,02           ;02 function for single digit display
        mov al,bl           ;copy ans in Al register
        and al,00fh         ; Mask the MSB. Since number is in LSB no need to
                            ; shift

        cmp al,09           ; check if number in 0-9
        jbe alpha2          ; if alphabet add additional 7 to make correct 
        add al,07           ;  ASCII value

alpha2:  add al,30h         ; add 30H for ASCII value
         mov dl,al          ; display content in DL for 02 function
         int 21h

         mov ah,4ch         ; 4ch function to terminate program and return  
         int 21h            ;  to DOS prompt

         end start
         end                ; end of file

Output

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