Occurrence of Letter(CASE INSENSITIVE)

This is Microprocessor code for Displaying the Number of times that letter repeated the string is read from keyboard using BIOS function...
Algorithm is:

1. Initialize Data segment
2. read string from keyboard
3. point 2 pointer SI and DI to starting of string.
4. One is used for checking individual character of string with other (DI)
5. the concept used is case conversion logic
6. If any Character is repeated Increment BL
7. After Checking with all the character display the result...

The code is as follows...

;Finding The Occurrence of Letter(CASE INSENSITIVE)
;Author: AKSHATH KUMAR
;------------------------------------------
printf macro msg
        lea dx,msg
        mov ah,09h
        int 21h
endm
;---------------------------------------------
data segment
msg1 db 10,13,"Enter the String:",10,13,"$"
str1 db 10h,?,10h dup(' ')
len dw 01h dup(0)
msg2 db 10,13,"$"
data ends
;------------------
code segment
assume cs:code,ds:data
start:
        mov ax,data
        mov ds,ax
        printf msg1
        lea dx,str1
        mov ah,10
        int 21h
        printf msg2
        mov bx,0h
        mov cx,0h
        mov bl,str1[1]
        mov str1[bx+2],"$"
        lea di,str1+2
        mov cl,bl
        mov len,cx
        lea si,str1+2
change:
        mov al,[si]
        cmp al,5bh
        ja next
        add al,20h
next:
        mov [si],al
        inc si
        loop change

        mov cx,len
again:
        mov al,ds:[di]
        push cx
        mov cx,len
        mov bl,0h
        lea si,str1+2
up:
   
        cmp al,ds:[si]
        jnz skip
        inc bl
skip:
        inc si
        loop up
        pop cx
        inc di
        add bl,30h
        mov dl,bl
        mov ah,02h
        int 21h
        loop again
        int 3h
code ends
end start

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