Why after i create the file my dosbox will shut down automatically?? any problem of my code?
.model small
.stack 100h
.data
msg1 db 10, 13, 10, 13, "Please select an item:",0Dh,0Ah,0Dh,0Ah,09h
db "1- Create File",0Dh,0Ah,09h
db "2- show data",0Dh,0Ah,09h
db "3- Exit",0Dh,0Ah,09h
db "Enter item number: "
db '$'
msg2 db 10,13,"Success Create$"
file db "test.txt"
handle dw ?
buffer dw 10 dup (?)
.code
main proc
mov ax,@data
mov ds,ax
ShowMenu:
lea dx, msg1
mov ah, 09h
int 21h
mov ah, 01h ;get choice
int 21h
cmp al, "1"
je CreateFile
cmp al, "2"
je ShowData
cmp al, "3"
jmp Quit
jl ShowMenu
Quit:
mov ah,4ch
int 21h
CreateFile:
mov ah,3ch ;create file
mov cx,0
lea dx,file;set file name
int 21h
lea dx,msg2
int 21h
jmp ShowMenu
ShowData:
mov ah,3dh ;open file
mov al,0 ;open as read only
lea dx,file
int 21h
mov handle,ax
;read one char
mov ah,3fh ;service to read file
mov bx,handle
mov cx,1 ;how many byte to read
mov dx,buffer ;where to store
int 21h
;close file
mov ah,3eh
mov bx,handle
int 21h
jmp ShowMenu
main endp
end main
create a text file
The problem of not setting the function code 09h before displaying the success message (comment by David Wohlferd) would normally just close your program but not the DOSBox emulator.
The handle that you get from creating a file would ordinarily leave AH=0 and that would subsequently invoke a DOS termination function.Terminate program
file db "test.txt" handle dw ?
A further problem in your program is that you forgot to zero-terminate the filespec:
file db "test.txt", 0
A garbage filespec could potentially make DOSBox shutdown!
Because the handle variable is defined with ? (uninitialized memory) you could be unlucky that the following byte does not happen to be a zero.