x86-16

I'm curious how many ways are there to set a register to zero in x86 assembly. Using one instruction. Someone told me that he managed to find at least 10 ways to do it. The ones I can think of are: xor ax,ax mov ax, 0 and ax, 0 There are a lot of possibility how to mov 0 in to ax under IA32... lea eax, [0] mov eax, 0FFFF0000h //All constants form 0..0FFFFh << 16 shr eax, 16 //All constants form 16..31 shl eax, 16 //All constants form 16..31 And perhaps the most strange... :) @movzx: movzx eax, byte ptr[@movzx + 6] //Because the last byte of this instruction is 0 and... @movzx: movzx ax, byte

I'm trying to display 0-9 diagonally in assembly, but the output puts my diagonally printed numbers in the middle of the window. Here is the code: start: mov ah, 02h mov cl, 0Ah ;counter (10) mov dx, 02h ;mov bx, 02h mov dl, 30h ;start printing 0-9 mov dh, 02h ;start row mov al, 02h int 21h again: int 10h int 21h ;add dx, 01h inc dh inc dx inc al loop again mov ax, 4c00h int 21h The output should be: 0 1 2 3 4 5 6 7 8 9 The current output prints that, but on the middle of the window. I've tried adding a new register bh and use it to put my cursor on my current position when I execute the file.

I am totally new in assembly language programming and I am stuck with a problem in which I need to change case of the entered string plus reverse the string as well. I am using emu8086. I the following code I am either able to change case or reverse the string. but I need to perform both the operations simultaneously. .MODEL CASECHANGE .DATA MSG1 DB 0DH,0AH, 'Enter string:$' MSG2 DB 0DH,0AH, 'String in reverse case:$' STR1 DB 255 DUP(?) .CODE START: MOV AX,@DATA MOV DS,AX LEA DX,MSG1 MOV AH,09H INT 21H LEA SI,STR1 MOV AH,01H jz offsets GET: INT 21H MOV BL,AL CMP AL,0DH JE SET XOR AL,20H MOV

I'm trying to use DOSBox with debug.exe on a 64-bit system. It works perfectly fine if I enter the commands manually. When I redirect input from a file with: debug < [file] it doesn't work. On every line except for the first it displays an error similar to this: DOSBox will eventually hang and crash. Is there any way to fix this? The input file I am trying to process as commands is: a 100 jmp 145 db 'Hello, World!', 0D, 0A, 'Press any key to continue . . .$' a 145 mov ah, 09 mov dx, 102 int 21 mov ah, 08 int 21 int 20 rcx 100 n hello.com w q Michael Petch I can reproduce the behavior you are

I wrote this code in emu8086 and it goes well in the emulator but when I'm trying to compile it with NASM it's throwing me up the error: "operation size not specified", help someone? add bx,[3565] sub bx,0xcc mov [bx],0CCh NASM can't figure out what you meant by a line like mov [bx],0CCh . Clearly, this sets something to 0CCh. But do you want to have bx pointing to a single byte , short, long, ...? This will manifest itself as the fairly self-explanatory error: operation size not specified in NASM. You could avoid the error specifying the type, as shown below: SECTION .text global start start:

I'm writing a DOS clone for a school project and I'm trying to read some sectors from a floppy drive (mainly the root directory of a FAT12 file system, sector 19) using BIOS INT 13, 2. I set the parameters right - or at least I think I do so - and then call INT 0x13 with AH = 2. Then, though, the system hangs. I can't figure why. I'm using the following code to call the interrupt: mov ah, 0x2 ;Read sectors function mov al, 1 ;I want to read one sector mov ch, 0 ;From track 0 mov cl, 2 ;Sector 2 mov dh, 1 ;Head 1 mov dl, [device_number] ;Obtained from BIOS during boot mov bx, 0x7C0 ;Buffer

I am coding a game in assembly 8086. I fixed the issue when the game didn't open, but I can't fix the controls. The ESC key works. When I press it, it goes to _QUIT function, but if any other key was pressed before that, the controls freeze and don't react on any key. Is there something wrong with my function? I tried to change the AL register to AH , but it didn't work. _KEYCHECK: mov ah,01h int 16h cmp al,1Bh ;ESC je _QUIT cmp al,48h ;UP je _PLAYER.UP cmp al,50h ;DOWN je _PLAYER.DOWN cmp al,4Bh ;LEFT je _PLAYER.LEFT cmp al,4Dh ;RIGHT je _PLAYER.RIGHT ret Your _KEYCHECK function is using the

I have a problem with the MASM32 assembler The following code is a Hello World example that I copied from the MASM32 tutorial: .model small .stack .data message db "Hello world!", "$" .code _main proc mov ax,seg message mov ds,ax mov ah,09 lea dx,message int 21h mov ax,4c00h int 21h _main endp end _main On attempt to assemble, MASM32 throws A2004 error with the following comment: C:\masm32\console.asm(11) : error A2004: symbol type conflict Can anyone help me with that? This code worked perfectly fine with the TASM assembler, but now I have to use MASM32 and I am having this A2004 error for

Possible Duplicate: ASM x86 integer overflow I get a divide error- overflow and am not sure why. Here is the complete code that reproduces the error include emu8086.inc org 100h mov ax, 2 mov bx, 10 div bx mov ax, 2 mov bx, 2 div bx ret Try adding xor dx, dx before each div and see if that doesn't help. Since you're specifying a 16-bit target, div divides dx:ax by that target. If dx starts out containing a large number (more accurately, anything but quite a small number), the result will overflow. Even if it doesn't overflow, your result won't just be ax / bx as you apparently intend. 来源：