Uppercase_to_lowercase.txt

section .data
    src_string db 'HELLO WORLD', 0
    dst_string db 50 dup(0)  ; Destination string with enough space

section .text
    global _start

_start:
    ; Initialize pointers
    lea si, [src_string]
    lea di, [dst_string]

convert_loop:
    lodsb               ; Load a byte from source into AL
    cmp al, 0           ; Check for null terminator
    je done             ; If null, exit

    ; Check if the character is an uppercase letter (A-Z)
    cmp al, 'A'
    jl not_uppercase
    cmp al, 'Z'
    jg not_uppercase

    ; If it's uppercase, convert it to lowercase (a-z)
    add al, 32
not_uppercase:
    stosb               ; Store the modified character in destination
    jmp convert_loop    ; Continue with the next character

done:
    ; Display the lowercase string
    mov ah, 0x0E        ; BIOS teletype function
display_loop:
    lodsb               ; Load a byte from destination string into AL
    cmp al, 0           ; Check for null terminator
    je exit             ; If null, exit
    int 0x10            ; Display the character
    jmp display_loop

exit:
    ; Halt the program
    hlt