Nasm int 21h bss var RESB 1 segment . asm -o test. When I'm in my directory, I run nasm -f prog1. May 7, 2010 · int 21h mov ax, 0x4c00 ; terminate program int 21h num1: db 10,20,30,40,50 total: dw 0 It uses Nasm syntax, but Linux. Not a bad idea to get some stuff working as a "dosless . In any case, printing a number by putting its value into edx is unlikely to work - _printf would be a better bet. I have experience programming with ARM, but now i'm stuck with the 0x10 interruption. May 1, 2012 · ;file: showmsg. here is my first assembly program: This doesn't address the problem you're actually having, the directory listing not working after int 21h/4Bh returns. When you've got that working, stuff it into a bootsector (preferably an already-working bootsector). com myfile. Mar 27, 2018 · DOS汇编程序：MOV啊，09h和int 21h组合不显示任何内容如何将 mov ah,1 int 21h 用于单个输入？ DOS INT 21H以nasm风格运行0AH 汇编中的“int 21h”是什么意思？在dos中编写使用INT 21H的8086汇编程序如何使用DOS中断21h / AH = 25h（设置中断向量）？ Jun 18, 2018 · start: mov ax,data mov ds, ax mov es, ax mov cx, size;cx will contain size,we need it to ; check if we have got 10 inputs from key board lea dx, Enter_string;it will display a text on screen to enter text mov ah, 9 int 21h call get_string;input string from keyboard mov ax, 4ch;terminating int 21h get_string: mov si, 0; si will be used as index Nov 16, 2023 · Additionally, the functions on BIOS int 13h deal with the disk as a physical entity, whereas the c:\users\user\folder directory that DOSBox mounted for you became the logical C: drive. As per the excellent Ralf Brown's interrupt list, the int 21, fn 0a call modifies that byte to be the actual count of characters read (sans carriage return). Example that uses segments:;- hello. Interrupts are similar to functions using CALL and RET, however parameters are usu-ally passed via registers and we use INT and IRET. " to call scanf in NASM assembly you need to: Jun 28, 2019 · If it is desired to use MSDOS memory management, the program first has to release the memory using INT 21H, AH=49H, ES=segment, BX=# paragraphs. Apr 29, 2005 · int 21h jc exit mov ah,9h ; spew "volume label" mov dx,vlmsg int 21h mov si,diskinfobuf+6 ; offset 6 into the buffer mov cx,11 ; 11 bytes of volume label showvl: lodsb int 29h loop showvl mov ah,9h ; spew a carriage return mov dx,crlf int 21h mov dx,snmsg int 21h mov ax,[diskinfobuf+4] call word2hex mov al,'-' int 29h mov ax,[diskinfobuf+2] Aug 8, 2011 · ; be loaded at 100h, but informs Nasm that; our file will be loaded by dos at 100h. start: ; or to be at the start of code segment. If you've switched to protected mode, bios interrupts won't work, and you'll have to go to ports. asm'. org 100h _start: ;LOGO mov ah, 9 mov dx, logo1 int 21h mov ah, 9 mov dx, logo2 int 21h ;MENU mov ah, 9 mov dx Oct 12, 2007 · Then I'd try displaying a string in other ways - int 21h, ah=40h - write to a file, using "stdout" - 1 - as a handle. May 14, 2012 · The interrupt 21h was the entry point for MS-DOS functions. Feb 23, 2011 · Use int 21h if it helps you. If not, let us know what did happen. What subfunction of Int 21h does the assignment use? Feb 27, 2013 · . text global start start: ; Getting command line arguments xor si, si xor ax, ax mov byte [st], 0 mov al, [ds:80h] ; Getting arguments' string length mov si, ax ; Storing in index register mov byte [ds:81h+si], 0 ; Adding string termination symbol ; Opening file mov dx, 82h ; Filename address Oct 23, 2011 · I need to prompt to user a msg that tells him to write a number , then I store this number and do some operation on it After searching in INT 21h I found this : INT 21h / AH=1 - read character from standard input, with echo, result is stored in AL. asm file content. Mar 12, 2020 · Would you do mov edx,file_name, it would compile without warning (but it would not work, because int 21h under linux doesn't work). MOV DL, 'A' MOV AH, 2 INT 21H. int 21H mov ax,4c00h int 21h main endp end main Hello World (NASM Linux)! SECTION . $" prompt4 db 0dh, 0ah, "Your number in octal is: $" section . mov ah, 6 mov dl, 255 int 21h; get character from keyboard buffer (if any) or set ZF=1. Oct 27, 2020 · INT 21H @START_2: ; jump label XOR BX, BX ; clear BX LEA DX, PROMPT_1 ; load and display the string PROMPT_1 MOV AH, 9 INT 21H MOV CX, 8 ; initialize loop counter MOV AH, 1 ; set input function @LOOP_1: ; loop label INT 21H ; read a character Jun 9, 2016 · MAIN PROC ;INITIALIZE DS MOV AX,@DATA MOV DS,AX cld ; tell "stosb" to forward MOV DI,1000H ; address where to string will be copied to MOV AH,01H ; int 21 function 1: read char with echo LOOP: INT 21H ; read a char from keyboard CMP AL,0DH ; stop if enter is pressed JE END stosb ; save al at DI and increase DI by one JMP LOOP END: mov [di], 0 INT 21 - DOS Function Dispatcher For more information, see the following topics: INT 21,0 Program terminate INT 21,1 Keyboard input with echo INT 21,2 Display output INT 21,3 Wait for auxiliary device input INT 21,4 Auxiliary output INT 21,5 Printer output INT 21,6 Direct console I/O INT 21,7 Wait for direct console input without echo INT 21,8 Wait for console input without echo INT 21,9 Print In MASM, you would use the INT instruction to call the interrupt, followed by the interrupt number in hexadecimal. – Ped7g Commented Nov 24, 2016 at 11:17 Jun 21, 2009 · org 100h mov dx,msg mov ah,9 int 21h mov ah,4Ch int 21h msg db 'Hello, World!',0Dh,0Ah,'$' Build this into a . data] ;section containing initialized data file db '*. text mov byte [temp1], 2 ; MAXINPUT - 2 mov ah, 0Ah mov dx, temp1 int 21h Apr 11, 2014 · ; Save as hello. Keith INT 21h / AH=0Ah - input of a string to DS:DX, fist byte is buffer size, second byte is number of chars actually read. mov ah, 6 mov dl, 'a' int 21h; output character. 01. dll. Dec 16, 2007 · int 21h mov ah,0xA mov dx,buff int 21h mov al,'$' mov bl,[count] mov bh,0 Nasm is presumed able to count. asm file to create the executable file prog1. It can then use INT 21H, AH=48H, BX=# paragraphs, to allocate memory. 表 Sep 28, 2012 · mov [input], al cmp al, 13 jz endwhile jmp while endwhile: mov ah, 9 ; displaying the input. asm" and produce a COM file as expected. Try displaying one character at a time. NASM and MASM •We will use NASM (Netwide Assembler) in this course •NASM is operating system independent –One of the two widely used Linux assemblers –The other is GAS (GNU assembler) •The syntax differs significantly in many ways from MASM (Microsoft Assembler) –MASM syntax is a standard that is almost always understood Oct 29, 2021 · ormat mz entry main:start stack 100h segment main start: mov ax, text mov ds, ax mov dx, hello call extra:write_text mov ax, 4c00h int 21h segment text hello db 'Hello world!', 24h segment extra write_text: mov ah, 9 int 21h retf FASM generates a MSDOS exe file and loading this in DEBUG I see the following: Jun 21, 2016 · I recently started learning assembly. DOS allows you to approach your logical drives on the sector level using int 25h (read) and int 26h (write). COM) ;nasm -fbin showmsg. com file that writes the message to 0B800h. At 15th line, I trying to output field_separator string, but get my . If you want to keep the same code you've got, just check "count" before you attempt to convert the second character. I suspect that I'm using the wrong register, or that I've Jul 26, 2023 · section . Logged nobody Guest; Re: print a string « Reply #1 on: March 17, 2008, 11:17:21 PM Mar 9, 2019 · a = 1; b = 2; c = "values are: " + a + " and " + b ; This data roughly translates to: a db 1 b db 2 c db "values are: ? and ?$" Your variables a and b are numbers. ', and have to be lowercase! ; To compile nasm code type:; nasm myprog. my issue is for some reason it always thinks it is A and i dont know why. But: Oct 22, 2016 · You may want to reload the second byte of buf each time through the loop, the one dictating how many of the previous characters can be processed from the buffer. Not only does it read only one key at a time, but the notepad-like hit detection makes it . asm" org 100h ; inform Nasm this is a . Don't forget that when the user enters 5 on the keyboard, DOS function AH=1 returns 35h in AL, which is not the value you should calculate with. The idea is to do something like this: mov bp, hexnum ; Get Aug 13, 2011 · int 21H jc eprint retn jmp terminate eprint: mov ah,9h mov dx,emsg int 21h terminate: mov ax, 0x4C int 21h [section . exe) org 100h segment . section . INT 21h Function 05h: Write Character to Default Pr inter Write the letter 'A': mov ah,05h ; select printer output mov dl,65 ; character to be printed int 21h ; call MS-DOS Write a horizontal tab: mov ah,05h mov dl,09h int 21h 3. com (or myprog. By the way i need to get single input character from user's keyboard (like when a program ask you for y/n ?) so as key pressed and without pressing enter i need to read the entered character. Jul 20, 2012 · There are many differences between NASM and MASM, and your code needs quite a bit of work to port. ; important for calculating where "msg" will be. com hello. asm" "ld -o hello3. com file. EXE program may or may not allocate all of the memory in the 640KB area. I wrote the following code: section . Apr 24, 2021 · ormat mz entry main:start stack 100h segment main start: mov ax, text mov ds, ax mov dx, hello call extra:write_text mov ax, 4c00h int 21h segment text The address of each ISR takes up 4 bytes, so when the processor encounters an "int" instruction, it multiplies the operand (21h, in this case) by 4, fetches the address of the ISR from the table (the Interrupt Vector Table -IVT), executes the code at *that* address, and returns to where it was. com that is created by NASM and an output listing file prog1. 0x07c0:0000 and 0x0000:0x7c00 both map to the same physical address 0x07c00 where the bootloader is loaded into memory by the BIOS. exe I am currently following this video on tutorials on NASM. Nov 30, 2009 · Most Unix systems and derivatives do not use software interrupts (except int 0x80) seems like a weird way to put it. text mov dx, variable ; address, no "[]"s! mov ah, 9 int 21h ret ; or int 21h/4Ch In an OS that supports dos, that ought to work. asm -o showmsg. Feb 5, 2019 · Hello everyone, i just started to learn programming with nasm. Thanks very much for the help Frank. this function does not add '$' in the end of string. com-u 0D81:0100 FF261101 JMP [0111] 0D81:0104 48 DEC AX 0D81:0105 6F DB 6F Feb 6, 2005 · int 21h In nasm, I have to preload ds: mov ax, data mov ds, ax mov ax, line mov dx, ax mov ah, 09h int 21h I compiling to an OBJ and linking to an EXE in Wind98. zip & nasm-2. if there is no character in the keyboard buffer, the function waits until any key is pressed. asm -o progm1. If you're really desperate to use interrupts in 32-bit code, int 80h will work in Linux. I'm trying to print a char value (to print an hexadecimal) using an array. text mov dx,msg mov ah,09 int 21h mov ax,4c00h int 21h Notice the spelling of the segment names! Nasm knows ". Feb 2, 2016 · Typically most bootloaders use ORG 0x7c00 or ORG 0x0000 and then set the DS register accordingly to start the bootloader. code main proc mov ax,@data ;define mov ds,ax mov ah,9 lea dx,nter ;output nter int 21h mov ah,10 lea dx,nam int 21h Apr 5, 2013 · 100% works. You need to convert these into text before inserting them in the string which, in this simplified example, uses the question mark character (? You could, if you like pain, do it "DEBUG-style", and do "mov dx, 109h", but Nasm is a symbolic assembler, and will understand "mov dx, temp1". data" and ". All three input methods described until now (in the above answer!) were clearly tailor-made to suit Microsoft tools like EDLIN. Jul 20, 2011 · If you just want to select a menu item, junk the "buffered input" routine, and use one of the "input one key" routines int 21h/2, 21h/7, or 21h/8, IIRC, or int 16h/10h, and just compare. Second: You should always use a documentation for the system calls (int 21h). data ;data section for initialised data & constants cr equ 0dh ;carriage return Nov 21, 2018 · INT 21H MOV BX, AX ;I store left range set in BX MOV AH, 1 INT 21H MOV DX, AX ;I put right set in DX MOV CX, DX SUB CX, BX INC CX ;CX has a number of numbers to check MOV DX, 0 JMP CHECK CHECK: CMP BX, [PRIME] JE ADPRIM CMP BX, [PRIME + 1] JE ADPRIM CMP BX, [PRIME + 2] JE ADPRIM CMP BX, [PRIME + 3] JE ADPRIM INC BX LOOP CHECK JMP WRITE ADPRIM: Dec 11, 2018 · I'm having a weird problem with my ASM code launched in DOSBox. com writeit. How about if we do: BUFSIZ equ 20 section . As noted in the comments, an . com', but all that happens is it skips a line and gives me another command prompt. text mov dx, prompt ; move your prompt into your data register mov ah, 9 ; use the print string function int 21h ; print your prompt mov cx, 0 ; set your counter register to 0 cld ; clear direction to process string left to right mov di, string1 ;set string1 as destination mov ah, 1 ;read char fcn int 21h ;read it Jan 12, 2020 · segment . But I wanted to Apr 24, 2017 · int 21h means, call the interrupt handler 0x21 which is the DOS Function dispatcher. e. int 21h ah 02h doesn't work for some reason. Does masm and the MS linker preload DS for me? Thanks for any explaination of the darkness of these assemblers. start: mov ax,DATA mov ds,ax mov ah,9 mov dx,text int 21h mov ax,4c00h int 21h SECTION DATA text db 'Hello,World',13,10,36;- hello. Jul 5, 2011 · org 100h ; tell Nasm where DOS will load us segment . com -f bin hello. code START: mov ax, data mov ds, ax finit call TABLE mov dx, TABNAM call MAKDAT xor dx, dx mov cx, Endtab*4 call WRITE call CLOSE mov ax, 4C00h int 21h TABLE: xor di, di ; Create sine table TAB: fldpi fimul DWORD[I] fidiv DWORD[TEIL] ; by 180(INT) fsin fstp DWORD[di] inc WORD[I] add di, 4 cmp WORD[I int 21h pop ax loop . com file ; int 21h is going to want mov dx,msg ; the address of or message in dx mov ah,9 : ah=9 - "print string" sub-function int 21h ; call dos services mov ah,4Ch ; "terminate program" sub-function int 21h ; call dos services Sep 28, 2019 · What is the use of mov ah,10 in int 21h. You should not use any sections, and specify org 100h to compensate for the load address. data ; data section msg: db "Hello World",10 ; the string to print, 10=cr len: equ $-msg ; len is a value, not an address SECTION . data variable db "5$" section . txt" msg: db "Even if you’re on the right track, you’ll get run over if you just sit there" len: equ $-msg segment . Please enter a number value. NASM - The Netwide Assembler » MOV AH,4Ch ; Set terminate option for int 21h INT 21h ; Return to DOS (terminate program) END Begin it is inexpected end of file Nov 28, 2013 · I am trying to implement the mouse functionality in my desktop application. His second edition uses dos, mostly, if you int 21h putch: push ax mov ah, 02h int 21h pop ax ret getch: push bx mov bh, ah mov ah, 08h int 21h mov ah, bh pop bx ret putline: push ax push bx mov ah, 0004ch int 21h pop ax pop bx ret getstring: call getch cmp dl, 0dh Jul 29, 2011 · [BITS 16] [ORG 0x0100] [SECTION . It is possible to print the result from calculating 1/7 with 9 decimal places and still only use integer operations. nasm -o hw. You must write the suffix "h" or the prefix "0x". asm bits 16 ; the default for "-f bin" anyway org 100h ; tell Nasm where dos is going to load us section . data print: add byte [var], 1h mov DL, [var] mov ah, 2h int 21h ret Jan 18, 2014 · DOS 汇编中，大部分工作依靠 21 号中断 (int 21h) 来完成，并且 BIOS 服务中断用 int 10h 和 int 16h ，在 linux 中，所有的函数通过 linux 系统调用最终被内核处理，并且通过 int 80h 陷入内核代替用户空间执行，这称为 linux 的软中断 (关于软中断，这里不细讲，我以后会 Sep 10, 2010 · int 21h But learning this the hard way was much more interesting as you can see and understand the steps it takes to create code like this. com hello3. com org 0x100 mov ax, cs mov ds, ax mov ax, str1 ;Transmit parameter to show_msg through AX call show_msg mov ax, 4c00h int 21h show_msg: ;the address offset of the string is stored in ax mov dx, ax ;DS:DX=string address mov ax, 0900h ;AH=09 int 21h ret str1: db "Hello, world!$" Terminal mov ecx, msg mov edx, msg_L int 80h mov eax, 1 ; EXIT COMMAND mov ebx,0 ; No Eror int 80h To compile it and execute I use: nasm -f win32 test. You'll need AH=09h to display the prompt. INT 21h / AH=7 Character input without echo to AL. Jan 2, 2025 · mov ax,3509h ; get INT 9 vector int 21h mov word ptr old_interrupt9,bx ; save INT 9 vector mov word ptr old_interrupt9+2,es mov ax,2509h mov dx,offset int9_handler int 21h; set INT 9 vector mov ax,3100h mov dx,OFFSET end_ISR shr dx,4 inc dx int 21h END start Here is my attempt at implementing in NASM syntax Dec 8, 2018 · 通常、int 00hからint 1fhまではハードウェア割り込みやbios用に、int 20hからint ffhまではソフトウェアルーチン用に用います。 MS-DOSでは、OSとしての処理を提供するルーチンを、割り込み番号21Hに割り当てています。 Jul 24, 2011 · int 21h;put write to file here mov dx , buffer mov cx, 512 mov bx, [handle] mov ah, 40h int 21h mov ah, 3eh ;Close file int 21h jmp stop stop: mov ax, 0x4C00 ; Terminate program int 21h buffer times 512 db 0 Filename db 'test. text START: mov ah, 9 ;Display input prompt mov dx, prompt1 int 21h mov bx, 0 ;Get input mov ah, 1 int 21h DEC_IN: cmp al, 0dh ;compare input to carriage return; check if user is finished je DEC_OUT ;if yes, go display the prompt cmp al, '0' ;compare to Nov 18, 2020 · int 21H dec cx jnz _loop1 mov ah, 4ch int 21h ; Main ENDP ; NASM doesn't support pseudoinstruction ENDPROC. com. 03. com',0x00 REAL_NAME times 13 db 0 DTA times 80h db 0 ;address to DTA emsg db 'cannot rename file$' thank you again for all the help Apr 14, 2014 · Using this dos call (INT 21H, the 21H not showing in the post), STRING+1 will contain the number of characters entered (not including the return key), and the entered data will start at STRING+2. The code written above prints the single character 'A' on the screen. com -l prog1. asm - (DOS exe file) --- cut here Assemble with Nov 28, 2013 · , HI, nasm, how do you write a program to convert a 10 digit binary number into decimal and to base 32 (0-9, A-V ) Requirement #1: Your program should clearly prompt the user with a message to enter an exactly 10 digit binary number, which you should store as a null-terminated string (i. get user input get_chars: mov ah, 01 int 21h ret ;display string display_string: mov ah Aug 14, 2012 · D:\Alfonso\AVCH>debug prueba2. These have to have the '. . Is your prompt even working with int 0F1h? If the original poster is still around (unlikely), and hasn't long since solved the problem (even less likely), what command-line did you give Nasm to assemble this, what OS are you running, and exactly what does the error-message say? Jan 26, 2009 · How are you getting your DOS program to execute in 32-bit mode, but still be able to use int 21h DOS calls? If the machine code actually executes in 16-bit mode, the 16-bit mov r16, imm16 instruction that decodes is a different length than the 32-bit mov r32, imm32 NASM emitted, so the high 2 bytes of the msg address would decode as an instruction. you ca org 100h mov dx,msg mov ah,9 int 21h mov ah,4Ch int 21h msg db 'Hello, World!',0Dh,0Ah,'$' Build this into a . top pop dx pop cx ret;-----;-----newline: push ax push dx mov ah, 2 ; print character in dl mov dl, 13 ; carriage return int 21h mov dl, 10 ; and linefeed int 21h pop dx pop ax ret;-----Besides giving us the remainders in the wrong order, "div" is dog slow. Apr 29, 2017 · I DW 0, 0 TABNAM DB "Sin. I have successfully implemented the custom boot loader which transfers the control to the desktop application. example: Oct 17, 2012 · int 21h mov dl, dh int 21h mov dl, ' ' int 21h pop dx pop cx pop ax %endmacro %macro print 1 push ax push dx mov dx, %1 mov ah, 9 int 21h pop dx pop ax %endmacro [org 100h] [section . COM. bss" if you have uninitialized data - you don't). You'll have to use the Windows API. lst also produced by NASM. text] Start: ; Get current interrupt handler for INT 21h mov AX,3521h ; DOS function 35h GET INTERRUPT VECTOR for interrupt 21h int 21h ; Call DOS (Current interrupt handler returned in ES:BX) mov WORD [v21HandlerSegment],ES ; Store the current INT 21h handler segment mov WORD [v21HandlerOffset],BX ; Store the int 21h mov ah,4Ch int 21h msg db "Hello, World!",0Dh,0Ah,'$' And then I assemble it with 'nasm -o hello. I googled it a lot but all what i found was somehow related to this line (int 21h) which result in "Segmentation Fault May 28, 2020 · The integer division div looses the fraction from calculating 1/7 because it can only store the integer part of the result in the EAX register. bss temp1 resb 4 ; better to "%define MAXINPUT 4" section . 04), trying to assemble codes with nasm or nasm I receive a lot of errors (almost in each line). Nov 4, 2011 · Recently I migrated all of my homeworks to Linux (Ubuntu 10. 5x5 might be a problem. to print using INT 21h / AH=9 you must set dollar character at the end of it and start printing from address DS:DX + 2. I haven't looked at the relevant code much. asm (. ). com hi. For example to print something on stdout you have to: mov ah, 09h ; Required ms-dos function mov dx, msg ; Address of the text to print int 21h ; Call the MS-DOS API entry-point The string must be terminated with the '$' character. text mov ECX, 5 mov byte [var], 30h label1: dec ECX jnz label2 mov AX, 0;4C00h int 21h label2: call print jmp label1 segment . Jan 15, 2013 · I'm trying to write calculator in NASM (Asembly). take linux gcc, search how to produce 32 bit binaries, and how to link 32b nasm object files against it, then you can call from assembly libc functions like printf and similar (the linux services are very limited, and even just simple things like printing decimal number require writing your own string formatter, so having libc functions Apr 10, 2014 · i am trying to get input from the user and then i would like to output some text depending on what the user put in. int 21H;;;;; SEGMENT data msg DB 'Hello I'm using nasm under ubuntu. org 100h; the subfunctions of int 21h go in ah; 9 writes a $-terminated string mov ah, 9; the address/offset of the string goes in dx mov dx, msg int 21h; the 4Ch subfunction exits back to dos mov ah, 4Ch int 21h May 16, 2017 · function call for printing a character on the screen and moving in ah and then "int 21h" causes your function (2) to be executed and whatever is in data register is to be printed. Then write your own input routine, replacing int 21h - a "dosless . Hint: you made mistakes on both calls. For example, to call interrupt 21h (the DOS interrupt), you would use the instruction INT 21h. And here is the demo on buffering input, given on the page of 144, C INT 21h / AH=0Ch - flush keyboard buffer and read standard input. Thanks for looking. Hope that Answered your question Jul 6, 2009 · ; nasm -f bin -o writeit. It will not be zero-terminated. I run it in DOSbox by just typing 'hello. 01-win32. Feb 23, 2011 · int 21h isn't going to be available until/unless you've got dos loaded. o -o test. To ; nasm -f bin -o myfile. – ecm Commented Jan 8, 2022 at 13:35 Dec 8, 2007 · int 21h;user presses key;something like this?;mov ah, 10h;mov al, 0;int 16h;compare value ie cmp or jmp?;if Esc key pressed exit;if not, show key or value and loop display message msg db 'Press one key or Esc',0Dh,0Ah,'$' Thanks in advance, maybe I'll get good enough sometime to help others out. Your "finalvar" doesn't look like a proper "executable parameter block" to me - just a single dword 0 - but I don't know if that's the problem or not. com executable so it will be loaded at cs:100h with all segment registers equal to each other (tiny memory model). Mar 14, 2015 · section . data max db Nov 22, 2024 · I'm working in NASM, for DOSBox, in 16-bit real mode. The DOS operating system uses interrupts, specifically interrupt 21h. 输出. asm [BITS 16] [ORG 0x100] mov ax,3D00h mov dx,filename int 21h ; check for errors here! jc exit mov bx,ax mov ah,3Fh mov dx,buffer mov cx,512 int 21h ; check for errors here! jc exit; at an equivalent point, "partcopy" apparently checks the; number of bytes actually read (in ax). 1. data: file_name: db "haneens_texts. Aug 11, 2011 · int 21h mov ah, 4Ch int 21h filename db 'C:\delete. mov ah, 0ah int 21h. – user786653 Commented Aug 31, 2011 at 15:50 Apr 4, 2012 · mov ax,cs ; moving code segment to data segment mov ds,ax mov ah,1h ; here I read from keyboard int 21h mov dl,al cmp al,'1' ; if 1 jump to LOADRUN1 JE LOADRUN1 cmp al,'2' ; if 2 jump to LOADRUN2 JE LOADRUN2 LOADRUN1: MOV AH,4BH MOV AL,00 LEA DX,[PROGNAME1] ; Not sure if it works INT 21H LOADRUN2: MOV AH,4BH MOV AL,00 LEA DX,[PROGNAME2] ; Not int 21h add dx,01h ;sub hex value 1 from dx jmp while ;jump to while next: mov dx,cr ;output new line mov dx,lf mov ax, 04c00h ;this function exits the program int 21h section . mov edx, name int 21h mov edx, StudentID int 21h mov edx, InBoxID int 21h mov edx, Assignment int 21h mov edx, version int 21h ret I am assembling this using NASM. model tiny . text ; code section global main ; make label available to linker main: ; standard gcc entry point movedx,len ; arg3, length of May 1, 2021 · Also revise DOS function and concentrate to the proper function identificator in AH before INT 21h. Jan 7, 2014 · INT 21h, AH 0Ch reads the last pressed key, but in a text-edition fashion. If you're still in 16-bit mode, you've got bios interrupts available. $' str3 db 0Ah, 'You Nov 18, 2020 · Hi Azrael998, Int 21h is dos only. Put a call number in a register (AH for DOS, EAX for Linux), and other args in other registers, then run a software-interrupt instruction. For what goes between the beginning and the end, you'll want Ralf Brown's Interrupt List - covers dos (and bios) interrupts, ports, and memory - most of what you'll need for dos programming: Jan 13, 2022 · int 21h ; tell 'em the number mov dx, numbuf int 21h; and the units mov dx, degrees int 21h mov ah, 2 mov dl, [result_units] int 21h; say Buhbye - enhancement - go again? mov ah, 9 mov dx, bye int 21h exit: mov ah,4Ch int 21h;-----; atof - converts ascii string to float; expects: si pointed to zero-terminated string Aug 11, 2011 · int 21h name db 'Johnny', '$' introduce: push ebp mov ebp, esp mov ah, 9 mov dx, str1 int 21h mov ah, 9 lea dx, [ebp+8] ; dx = argument1 int 21h pop ebp ret str1 db 'My name is ', '$' I'm certain that the problem with this code is when using the LEA instruction, though i still cant figure the correct way to use it in my code. Good luck. Jr. Linux could use sys_write to write one or more assesterisk on the screen. mov ah, 09h int 21h. Mar 15, 2014 · I am trying to use nasm to rewrite assembly programs in "IBM PC ASSEMBLY LANGUAGE AND PROGRAMMING" (15th edition) by Peter Abel. Dec 1, 2015 · NASM assumes you want to move a single byte because mov cx, 1 int 10h jmp petla F1: mov byte [kolor], 0111b int 21h jmp petla F2: mov byte [kolor], 1001b int 21h NASM: cdecl calling convention int add(int a, int b) { return a+b; } push b push a call add add esp, 8 INT 21h XOR AX, AX MOV AL, DH ; second CALL show_integer Nov 27, 2004 · int 21h ;ok, print it mov ah,4Ch ;now prepare program shutdown int 21h ;do it msg db 'Hello, World!',0Dh,0Ah,'$' ;the message we are about to display May be this is XP specific, or did any have a similar problem in other Win32 versions? NASM - The Netwide Assembler » NASM Forum » int 21h mov ah,0Ah lea dx,buf1 int 21h lea esi,buf1+2 xor ecx,ecx mov cl,byte ptr [buf1+1] call _AsciiToSignedInt Aug 26, 2008 · I downloaded the nasm-2. 输入. It requires a "special" buffer - a byte for "max length", and a zero byte to return "length entered", your entered text will begin at buffer + 2. code org 100h mov dx,msg1 mov ah,09h int 21h here: mov ah,0Ah mov dx, len int 21h mov ah,02h mov dl,10 int 21h mov dl,13 int 21h mov bx,act mov dx,buffer add dl,byte [bx] mov bx,dx mov byte [bx],24h jmp comp yep: mov dx,g1 mov ah,09h int 21h mov dx,buffer int 21h mov dx,g2 int 21h mov ax, [i] call cond mov ah,02h mov dl,bh int 21h mov Dec 11, 2012 · No. (Whether this makes it harder or easier to use is a matter of opinion, I guess!) Both the BIOS interrupts and int 21h (and other dos interrupts) are 16-bit code, and won't work once we've switched to 32-bit protected mode. See: See: Apr 10, 2010 · int 21h mov ah,4Ch int 21h msg db 'Hello, World!',0Dh,0Ah,'$' I compiled and runned on Console liek this: Code: You suppose to write nasm hw. txt',0 Untested! Best, Frank Dec 27, 2015 · int 21h jmp exit even: mov ah,09h mov dx, even_msg int 21h jmp exit exit: mov ah,00h int 16h ret when i use this code, it only accepts numbers from 0 to 9, because ii used the funtion 01h in int 21h, but when i chang it to the function 0Ah in int 21h, even tho it accepts all numbers no matter how many digits are in it, it always says that it's Nov 25, 2008 · mov ah,040h ; the Write-to-a-file function for int 21h mov bx,1 ; the file handle for standard output mov cx,[msg_len] ; number of bytes to write mov dx,msg ; address of our "buffer" to write from int 021h ; call on Good Old Dos; now, lets read from a file that's already open, mov ah, 01h int 21h. ; END Main ; NASM requires the entry point labeled . We started out with some as86 bootsector code, and somehow slid into a dos . o" produces a COM file that prints no correct output. tab" segment . I'm using NASM assembly under windows and ALINK linker. Every operating system has different requirements. CR equ 0DH LF equ 0AH main: mov DL, 'A' while1: mov AH,02H ;print character int 21H mov BL, DL ;store the value of DL before using DL for print new line mov DL, 10 ;printing new line mov AH, 02h int 21h mov DL, 13 mov AH, 02h int 21h mov DL, BL ;return the value to DL cmp DL, 'Z' je exit add DL, 1 ;store in DL the next character jmp while1 exit: mov AH,4CH int 21h Apr 11, 2005 · I prefer int 21h/4Ch. May 19, 2018 · int 21h ; tell 'em the number mov dx, numbuf int 21h; and the units mov dx, degrees int 21h mov ah, 2 mov dl, [result_units] int 21h; say Buhbye - enhancement - go again? mov ah, 9 mov dx, bye int 21h exit: mov ah,4Ch int 21h;-----; atof - converts ascii string to float; expects: si pointed to zero-terminated string May 19, 2018 · int 21h ; tell 'em the number mov dx, numbuf int 21h; and the units mov dx, degrees int 21h mov ah, 2 mov dl, [result_units] int 21h; say Buhbye - enhancement - go again? mov ah, 9 mov dx, bye int 21h exit: mov ah,4Ch int 21h;-----; atof - converts ascii string to float; expects: si pointed to zero-terminated string Windows provides a very "rich" set of routines, compared to either int 21h or int 80h. int 16h is the one that handles the keyboard. Running this command gives me the following Sep 21, 2014 · int 21h; mov ah,09 ; display string mov dx,cr_lf; display carriage return and line feed int 21h; mov ah,09 ; display string mov dx,buf + 2 ; display string starting from address of buf (+ 2!) int 21h; int 20h; Untested(!), but I think that'll do better. That's how I'd approach it, anyway Jan 22, 2008 · Hi, I used fasm, whi won't it work when assembled :) thx;/* org 100h __entry_point: pushf mov ah,09h mov dx,message int 21h mov ah,08h Operating systems provide different mechanisms for using the operating system facilities. code org 100h start: ; Inicializando la fecha para LotusWorks mov ax, 2A21h int 21h mov [Reg_DX], dx sub cx,064h mov [Reg_CX], cx ; saving old interrupt vector mov ax, 3521h int 21h mov [old_int21h], bx mov [old_int21h + 2], es ; setting new interrupt vector cli push ds push cs pop ds lea dx, myint21h mov ax, 2521h int 21h pop ds sti ; TSR mov dx, 00ffh mov ax, 3100h int 21h Dec 17, 2014 · Depending on what you want to do, creating a com file directly using nasm is a simple option. o hello. zip this morning, and compile the hello. Look at Ralf Brown's interrupt list for DOS: Int 21/AH=09h and Int 21/AH=0Ah and check if you fulfilled all conditions (register usage, memory defines etc. In theory, the mechanism is the same. I also added . – rcgldr Jan 8, 2022 · int 21h is a DOS system call, int 80h is a 32-bit Linux system call, syscall is apparently a 64-bit MacOS system call (may also be used by other systems). Sep 22, 2004 · ; assemble with "nasm -f bin -o hi. com file" before you try to load it from a bootsector, so here's a . Mar 17, 2008 · NASM Forum » Using NASM » print a string int 21h ret pls help. Logged Andy. com file". Commenting out the first line and compiling with "nasm -f coff -o hello3. data msg db 'hello word$' segment . Mar 13, 2013 · org 100h mov ah, 09h ; print function mov dx, offset nameprompt int 21h mov ah, 0ah ; buffered string input mov dx, offset buffer int 21h mov ah, 09h mov dx, offset crlf int 21h mov dx, offset yourname int 21h xor bx, bx mov bl, buffer[1] mov buffer[bx+2], '$' mov dx, offset buffer + 2 int 21h mov ax, 4c00h int 21h buffer db 255,0,255 dup(0 Well, I'm confused, Codeferever. Member; Posts: 2; Re May 2, 2012 · RTFM on that int 21h/0Ah. asm - (DOS exe file) --- cut here SECTION CODE. , 11 characters total). lst in an attempt to use the prog1. text global _start _start: ; Print the message to the screen mov ah, 9 ; AH=9 means "print string" function mov dx, hello ; Load the offset address of 'hello' into DX int 21h ; Call the DOS interrupt 21h to execute the function ; Exit the program mov ah, 4Ch ; AH=4Ch means "exit" function xor Jan 31, 2005 · int 21h I can compile this with "nasm -o hello3. If you want to port that MASM code to NASM, see MASM/NASM Differences or the NASM documentation or google "NASM vs MASM" TL;DR: you are writing MASM code, not NASM. exe in the directory that I'm working with here. o ld test. asm in DOS prompt directly. Sep 22, 2001 · Nasmw is the same as nasm, only nasmw is a Windows program. asm -fbin -o myprog. Example: ORG 100h lea dx, [msg] mov ah,9 int 21h mov ax, 4c00h int 21h msg: DB 'HELLO WORLD$' Jun 11, 2012 · mov ah, 3fh mov dx, input int 21h input rb 100d And whatever you type in will the placed at the address of "input. Why does using "int 21h" on Assembly x86 MASM cause my program to crash? 2. 2. txt', '$' edit: I added some messages to the code so the user knows wheter the delete function worked or not. Mar 29, 2020 · segment . The int 0x80 i386 Linux system call ABI is extremely similar to the DOS int 0x21 ABI. Aug 23, 2011 · int 21h mov ah, 1 int 21h mov ah, 9 cmp al, 37h jz age_same jg age_older jl age_younger jmp after age_same: mov dx, str2 int 21h jmp after age_older: mov dx, str3 int 21h jmp after age_younger: mov dx, str4 int 21h jmp after after: mov ah, 4Ch int 21h str1 db 'ENTER YOUR AGE: $' str2 db 0Ah, 'Wow. 一般是这样的使用方式。通过这样两条指令，输入的字符就会被存储在al中。例如：在很多时候我们想要去做汇编程序的输入与输出（从键盘上直接的输入）并且屏幕上能显示的那种，我们就可以. I am wanting to extract things into several source files in the future. I present a shortened version of my program in order to be simpler to revise and anderstand. Best, Frank. bss: segment . You and I are the same age. Is the code right? I just got it from here. For consistency with int 21h, you should choose "h" Uses int 21h, not 0F1h, AFAIK I don't have much experience with it. We could do the same. Sep 24, 2013 · So I've started learning 16 bit assembly using NASM on a Windows machine. data hello db 'Hello, World!', 0 section . Oct 20, 2017 · I. Mostly we use like mov ah,0a for string input but why mov ah,10?. In NASM, you would use the int instruction, followed by the interrupt number in decimal. I made a working hello world code in console using win32 functions from kernel32. the "mov ah,01h" is setting AH with 0x01, which is the Keyboard Input with Echo handler in the interrupt. nter db 'enter you name:$' nam db 50,0,50 dup('$') ;num is 50, num + 1 is 0, num + 2 is 50 lfcr db 10,13,'$' ;line feed carrier return/next line carriage return . Best, Frank Aug 4, 2015 · I have nasm. Mar 2, 2012 · int 21h mov ah,4Ch int 21h Table db '0123456789' org 100h ; tell Nasm where dos will load us See if that helps. Both BIOS and dos interrupts are 16-bit code, and just won't work in 32-bit code. asm, assemble with nasm -f bin -o hello. text: global _start _start: mov edx,0777 mov ecx,2 mov ebx,file_name mov eax,5 int 21H mov eax,1 mov ebx,file_name mov ecx,msg mov ebx,1 mov eax,4 int 21H mov eax,1 mov Apr 5, 2018 · I'm learning assembly (FreeDOS, 16 bits) and I have an issue. entry: AL = number of input function to execute after flushing buffer (can be 01h,06h,07h,08h, or 0Ah - for other values the buffer is flushed but no input is attempted); other registers as appropriate for the selected input function. EXE and COMMAND. asm ORG 256 Start: JMP Main strOfs DB 'hello, world',0Ah strLen EQU $-strOfs Main: MOV SI,strOfs MOV CX,strLen SUB BX,BX ; clear videopage number and color MOV AH,0Eh ; BIOS function TELETYPE OUTPUT CLD nextChar: LODSB ; load AL from [SI], increment SI INT 10h ; Display one Apr 9, 2010 · Besides, I don't like stopping system until generating an interruption, I prefer to use a variable to be changed in the Int 08h that I will intercept. I'm doing a little program to verify the Bios interrupt set. If you used ORG 0x0000 you'd have to set DS to 0x07c0, if you use ORG 0x7c00 you'd set DS to 0x0000. We all know "dos uses int 21h" but int 29h is also fun and simple - prints the character in al, simple as that (unfortunately, it can't be redirected). INT 21h Function 09h: Write a $-terminated string t o standard output Nov 12, 2024 · org 100h start: mov ah, 1 xor cx, cx input: int 21h cmp al, '+' jz sum push ax inc cx jmp input sum: mov bp, sp ; bp points to stack top xor ax, ax ; initial sum is 0 jcxz print ; skip if no characters entered sum_loop: add al, [bp] ; add low byte only ; hint: you also can `adc ah, 0` here to get 16-bit sum in ax add bp, 2 ; next 16-bit word Apr 25, 2017 · @Moon: int 21h is the interface for 16-bit DOS, 32-bit linux uses int 80h and x86_64 uses syscall (for a quick example see here) or search SO for one of the many other threads. This is my first NASM program, just a simple, DX=pointer to '$' terminated string int 21h mov al,0 ; return code (0 = no error) mov ah,4Ch ; "EXIT" - TERMINATE Inputting text using int 21h AH=08h. intel_syntax in first line. text] print Text1 mov dx, Input mov ah, 0Ah int 21h mov si, Input+2 mov al, byte [si] and al, 0Fh jz @Fin May 7, 2019 · mov AH, 3F ; AH=3F=read mov BX, in_handle mov CX,60 Int 21H The function number that you move to AH is the hexadecimal number 3Fh. int 21h ret;Display character Display2: mov ah,02h int 21h ret;Input character Input: mov ah,07h int 21h ret Print_num: mov cl,8 ; cl counts the number of bits in the byte that has been read Print: cmp cl,0 ;if cl=0,then every bit in this byte has been read, je Next ;then jump to Next to get next byte DOS INT 21H Function 0AH in nasm style. text" (and ". dfp dkcdcp idjny eley ythzn fdnujex lffo wcflmg nwipj pidng

Nasm int 21h. Hint: you made mistakes on both calls.