;**********************************************************************************************
;*                                                                                            *
;*              LAB3-5.ASM - Assembler Laboratory ZMiTAC                                      *
;*                                                                                            *
;*            program that copies characters between files                                    *
;*                                                                                            *
;**********************************************************************************************

comment %
*********************************************
* copy bytes from one file to other file    *
*********************************************
%

.model small

.stack 512

.data
file1   db "filein.txt", 0
file2   db "fileout.txt", 0

.data?
buffer	db 1024 dup (?)

.code
start:
        mov ax, seg file1
        mov ds, ax
        ; open input file
        mov dx, offset file1    ; DS:DX - ASCIIZ of filename
        mov ah, 3Dh             ; open file
        mov al, 0               ; open for reading
        int 21h                 ; call DOS function
        jc open_error           ; CF set -> error
        mov si, ax              ; file handle in si
        ; create output file
        mov dx, offset file2
        mov cx, 0               ; file attributes: none
        mov ah, 3Ch             ; create file
        int 21h
        jc create_error         ; CF set -> error
        mov di, ax              ; file handle in di
        mov ax, seg buffer
        mov ds, ax

copy_loop:
        mov dx, offset buffer
        ; read block
        mov bx, si              ; source handle
        mov cx, sizeof buffer
        mov ah, 3Fh             ; read data
        int 21h
        jc loop_error
        cmp ax, 0
        jz loop_error           ; nothing to write
        ; write block
        mov bx, di              ; destination handle
        mov cx, ax
        mov ah, 40h             ; write data
        int 21h
        jz loop_error           ; write error
        ; write '*'
        mov ah, 02h
        mov dl, '*'
        int 21h                 ; write character

        jmp copy_loop

loop_error:
        mov ah, 3Eh             ; close output file
        mov bx, di
        int 21h

create_error:
        mov ah, 3Eh             ; close input file
        mov bx, si
        int 21h
open_error:
        mov ax, 4C00h           ; exit
	int 21h
end start