upper_to_lower.asm

      ;case conversion (UPPER -> LOWER)
         
       .model small
       .stack 100h
       .data 
            
           up db 'Upper: $'
           low db 'Lower: $'
           a db ?    
           
       .code
       
            main proc 
                
               mov ax,@data
               mov ds,ax
               
   LOOP:       mov ah,09h       ;output string
               lea dx,up
               int 21h
               
               mov ah,01h       ;input char
               int 21h
               mov a,al         ;move input into a
               mov cl,a
               add cl,32        ;convert to lower
               
               mov ah,02h       ;char print
               mov dl,09h       ;tab
               int 21h
               
               mov ah,09h       ;string print
               lea dx,low
               int 21h
               
               mov ah,02h       ;char print
               mov dl,cl        ;output
               int 21h
               
               mov dl,0Ah       ;newline
               int 21h
               mov dl,0Dh
               int 21h                     
               
               jmp LOOP
  
            main endp
            end main
                
                    
            
                

Case Conversion of character input (UPPER -> lower)