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flat assembler > Windows > MBR user input

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SC0U7



Joined: 20 Feb 2018
Posts: 13
Hello i use this code as MBR
but i try use some C functions to get user input but without issue can someone help me with get user input like this :
Enter your name: Peter
If user string equals Peter then show text Hello PPPeter!

thanks for any advices Smile


Code:
CPU 386
BITS 16
org 0h 


start:                                                                
        
        jmp short load_prog     
        ident   db "ONETOLVE"
                                
        
load_prog:

        cld
        xor ax,ax
        mov ss,ax
        mov sp,7c00h                                    ; setup stack
                
        mov ax,8000h
        mov es,ax                                               ; initialize es w/ 8000h
        mov ds,ax                                               ; initialize ds w/ 8000h
        
        
;
;       Load 6 sectors at es:0000
;

load_1:
        mov ax,0206h                    ;function/# of sec to read
        mov cx,0001h                    ;0-5 sec # (counts from one), 6-7 hi cyl bits
        mov dx,0080h                    ;dh=head dl=drive (bit 7=hdd)
        mov bx,0h                       ;data buffer, points to es:0
        int 13h
        cmp ah,0
        jne load_1                      ;this is allowable because it is
                                                                        ;relative
        
;
;       Jump to code at es:prog_continue
;
        
        push es
        mov ax,prog_continue
        push ax
        retf
        

        
prog_continue:
        
        mov ax,3
        int 10h                                                 ; clear screen
        
;
;       Display the null terminated message located at 0800:0400
;

        
        mov bp,0400h
        mov ah,0eh
        mov si,0ffffh
        
write_char:
        inc si
        cmp byte [ds:bp + si],0                 ; keep writing until there is a null byte 
        jz wait_for_key

        push bp
        
        mov al, [byte ds:bp + si]
        mov bx, 07h
        int 10h                                                 ; teletype the character
        
        pop bp
        
        jmp write_char
        
;
;       Wait for key
;
wait_for_key:
        mov ah,0
        int 16h

;
;       Copy 512 bytes from ds:0200 to 0000:7c00
;       Jump to 0000:7c00h
;

        mov cx,0200h                                    ; 512 bytes
        mov si,0200h                                    ; src location
        xor ax,ax
        mov es,ax                                               ; dest segment
        mov di,7c00h                                    ; dest addr
        rep movsb
                                                ; move 512 bytes

        
;
;       And we're done... jump to the real boot sector
;
;       mov dx,0080h                                    ;BIOS function
;       xor ax,ax
;       push ax
;       mov ax,7c00h
;       push ax
;       retf


times 1beh-($-$$) db 0
        ;ok.. a fake partition table. Who cares.
        db 80h                                   ;active
        db 0,0,0
        db 55h                                   ;fake
        times 59 db 0            
MBR_signature:
        db 55h,0aah
    
Post 28 Aug 2018, 13:18
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DimonSoft



Joined: 03 Mar 2010
Posts: 419
Location: Belarus
I’d start with the fact that AX is not guaranteed to be preserved during BIOS calls.

To help you further we need to know what goes wrong, i.e. what happens not the way you expected. Don’t expect anyone to bother to actually set up proper environment to run the bootloader.
Post 28 Aug 2018, 20:47
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