Untitled

.model small
.stack 100h
.data
    file_name db "input.txt", 0
    output_name db "output.txt", 0
    new_word db "new_word", 13, 10, "$"
    file_hand dw 0
    output_file_hand dw 0
    counter db 0
    buffer db 1 dup(0), "$"
    buffer2 db 10 dup(0), "$"
.code

Pradzia:
    mov ax, @data
    mov ds, ax

open_file:
    mov ah, 3dh ; opening file
    mov al, 0
    mov dx, offset file_name
    int 21h
    mov file_hand, ax
open_output_file:
    mov  ah, 3ch
    mov  cx, 0
    mov  dx, offset output_name
    int  21h
    mov output_file_hand, ax
reading:
    mov bx, file_hand
    mov ah, 3fh
    mov al, 0
    mov cx, 1
    mov dx, offset buffer
    int 21h
    mov file_hand, bx ; updating file_hand
    
checking:
    mov al, ds:[buffer]
    cmp al, 77h ; comparing to letter 'w'
    je reading_word
    jmp printing_symbol
    jmp reading
    
reading_word: ; checks if 3 continuing bytes make "word"
    mov bx, file_hand
    mov ah, 3fh
    mov al, 0
    mov cx, 3
    mov dx, offset buffer2
    mov file_hand, bx ; updating file_hand
    mov al, ds:[buffer2 + 1]
    cmp al, 6fh ; comparing to letter 'o'
    inc counter
    mov al, ds:[buffer2 + 2]
    cmp al, 72h ; comparing to letter 'r'
    inc counter
    mov al, ds:[buffer2 + 3]
    cmp al, 64h ; comparing to letter 'd'
    inc counter
    ;if "word" found
    cmp counter, 3
    je printing_string
    jmp reading
    
    exit:
    mov ax, 3eh ; closing files
    mov bx, file_hand
    int 21h
    mov ax, 3eh
    mov bx, output_file_hand
    int 21h

    mov ah, 4ch
    int 21h

printing_string:
    mov  cx, ax  ;STRING LENGTH.
    mov  ah, 40h
    mov  bx, output_file_hand
    mov  dx, offset new_word
    int  21h
    mov  output_file_hand, bx
    ret
printing_symbol:
    mov  cx, 1
    mov  ah, 40h
    mov  bx, output_file_hand
    mov  dx, offset buffer
    int  21h
    mov output_file_hand, bx
    ret

end Pradzia