; this sample gets a string from a user, then it prints it out. 
; this example uses dos interrupt: 21h 

name "int21"

org  100h

jmp start


; when no file path is specified the default file path is: 
;   c:\emu8086\MyBuild 

; if path is specified, it is emulated in: 
;   c:\emu8086\vdrive\ 
; for example, c:\test.txt is c:\emu8086\vdrive\c\test.txt 
; this is done to prevent disasters and accidental overwriting of valuable files. 
; relative paths such as "c:\mydir\..\autoexec.bat" are disabled for the same reasons. 


; declarations: 

; buffers hold ascii chars for INT 21h/0Ah input function, 
; first byte is its maximum size, second byte: actual size. 

; format of INT 21h/0Ah input buffer: 
;  -byte-offset-     -number-of-bytes-             -description-  
;      00                  1                        buffer size 
;      01                  1                        number of characters actually read (excluding cr). 
;      02             1 to buffer-size              actual buffer contents (including cr).  

s1        db 100,?, 100 dup(' ')
t2        db 100,?, 100 dup(' ')
filename  db 30,?, 30 dup(' ')   ; file name should be in 8.3 - dos compatible format. 


; file handle: 
handle   dw   0


; set segment registers to code: 
start:  mov ax, cs
        mov ds, ax
        mov es, ax

jmp m1
msg1    db  "enter any text: $"
m1:     mov dx, offset msg1
        mov ah, 9
        int 21h
; input a string: 
        mov dx, offset s1
        mov ah, 0ah
        int 21h



jmp m2
msg2    db  0Dh,0Ah,"enter file name: $"
m2:     mov dx, offset msg2
        mov ah, 9
        int 21h
; input filename: 
        mov dx, offset filename
        mov ah, 0ah
        int 21h

; set 0 to the end of the filename: 
        xor bx, bx
        mov bl, filename[1]  ; get actual size. 
        mov filename[bx+2], 0

; create new file: 
        mov cx, 0
        mov ah, 3ch
        mov dx, offset filename+2
        int 21h
        jc  error
        mov handle, ax
; write buffer to file: 
        mov ah, 40h
        mov bx, handle
        mov dx, offset s1+2
        xor cx, cx
        mov cl, s1[1]
        int 21h
        jc  error
; close file 
        mov bx, handle
        mov ah, 3eh
        int 21h
        jc error



; open existing file: 
        mov al, 0     ; read. 
        mov ah, 3dh
        mov dx, offset filename+2
        int 21h
        jc  error
        mov handle, ax
; read bytes from file 
        mov ah, 3fh
        mov bx, handle
        xor cx, cx
        mov cl, t2[0]
        mov dx, offset t2[2]
        int 21h
        jc error
        mov t2[1], al
; close file 
        mov bx, handle
        mov ah, 3eh
        int 21h
        jc error
jmp m3
msg3    db  0Dh,0Ah,"read from file: $"
m3:     mov dx, offset msg3
        mov ah, 9
        int 21h
; set '$' to the end of the buffer: 
        xor bx, bx
        mov bl, t2[1]        ; get actual size. 
        mov t2[bx+2], '$'
; print the buffer: 
        mov dx, offset t2[2] ; skip 2 control bytes. 
        mov ah, 9
        int 21h


        jmp ok

; print error message: 
error:  jmp m5
        msg5    db  0Dh,0Ah,"error...",0Dh,0Ah,'$'
        m5:     mov dx, offset msg5
                mov ah, 9
                int 21h


ok:
jmp m4
msg4    db  0Dh,0Ah,"press any key...",0Dh,0Ah,'$'
m4:     mov dx, offset msg4
        mov ah, 9
        int 21h
        mov ah, 0
        int 16h


; exit to the operating system: 
        mov ah, 4ch
        int 21h