code_seg segment para public

assume cs:code_seg,ds:data_seg,ss:stack_seg

;CR
;Carriage return and line feed
cr proc
    push ax
    push dx
    mov  ah, 02h
    mov  dl, 10
    int  21h
    pop  dx
    pop  ax
    ret
cr endp

;Show message
;Prints string from offset in dx
message proc
    push ax
    mov ah, 09h
;   mov dx, offset src_msg
    int 21h
    pop ax
    ret
message endp

get_file_path proc
    push ax
    push bx
    push cx

    mov ah, 3fh ;Read file DOS function
;   mov dx, offset source
    mov cx, 256
    mov bx, 0   ;Reading from STDIN
    int 21h

    call cr

    pop cx
    pop bx
    pop ax

    ret
get_file_path endp

open_source proc
    push ax

    mov ah, 3dh
    mov al, 0
    int 21h

    jc no_src ;If CF is set, then something is wrong with file, GTFO

    mov ,ax

no_src:
    pop ax
    ret

open_source endp

open_dest proc
    mov ah, 3dh
    mov al, 0

    ret
open_dest endp

start:
;Populating segment adresses
    mov ax, data_seg
    mov ds, ax
    mov ax, stack_seg
    mov ss, ax

    mov dx, offset source
    call get_file_path
    call open_source
    jc exit ;Returned from open_source, if CF is set, then exit

    mov dx, offset dest
    call get_file_path
    call open_dest

    ;exit
exit:
    call cr
    mov ah, 4ch
    int 21h

code_seg ends

data_seg segment para public
    source db 257 dup (0dh)
    dest   db 257 dup (0dh)

    buffer db 514 dup (0h)

    src_desc dw 1 dup (0h)
    dst_desc dw 1 dup (0h)

    src_msg db 'Enter source file name: $'
    dst_msg db 'Enter destination file name: $'
    no_src_msg db 'Something wrong with source file.'
data_seg ends

stack_seg segment para stack
    db 255 dup("!")
stack_seg ends

end start