Category Archives: Assembler

assembler

Windows – WinDbg tool.

WinDbg is very useful when you develop software with assembly language. You can install WinDbg using PowerShell by opening PowerShell as an administrator and running this command:

PS C:\WINDOWS\system32> Add-WindowsCapability -Online -Name WinDbg

1	PS C:\WINDOWS\system32> Add-WindowsCapability -Online -Name WinDbg

You can download it from the Microsoft store.

Programming with FASM – reading from file.

In the last article tutorial, I wrote about how to write a message to a text file named file.txt. Now, I will show you how to read that message. You must use the ReadFile function defined after fileapi.h, in WIN32AX.INC. The text is shown in modal dialog – has some limitations in terms of mode… Read More »

Programming with FASM – writing to file.

In this simple example, I will show how to write a file using the assembly programming language with FASM, known as flat assembler. You can use the FASM editor with the FASMW.EXE executable. Open this editor and use this commented source code:

;define format of exe file
format pe console 4.0
;include file WIN32AX
;http://flatassembler.net/docs.php?article=win32
include 'INCLUDE/WIN32AX.INC'
; define data for code
.data
 ;this will be the filename of file
 filename db 'file.txt',0
 ; this string will be write on the file
 buffer_text db 'This is a test by Catalin!'
 ; this is the size for WriteFile based on buffer_text
 buffer_size = $ - buffer_text
 ; define a space
 bytes_to_write dd ?
; the code for running
.code
 main:
 invoke  CreateFile,filename, GENERIC_WRITE, 0, 0, 4, FILE_ATTRIBUTE_NORMAL, 0
 ;https://learn.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-writefile
 invoke  WriteFile, eax, buffer_text, buffer_size, bytes_to_write, 0
 ;https://learn.microsoft.com/en-us/windows/win32/api/processthreadsapi/nf-processthreadsapi-exitprocess
 invoke  ExitProcess, 0
.end main

;define format of exe file

format pe console 4.0

;include file WIN32AX

;http://flatassembler.net/docs.php?article=win32

include 'INCLUDE/WIN32AX.INC'

; define data for code

.data

;this will be the filename of file

filename db 'file.txt',0

; this string will be write on the file

buffer_text db 'This is a test by Catalin!'

; this is the size for WriteFile based on buffer_text

buffer_size = $ - buffer_text

; define a space

bytes_to_write dd ?

; the code for running

.code

main:

invoke CreateFile,filename, GENERIC_WRITE, 0, 0, 4, FILE_ATTRIBUTE_NORMAL, 0

;https://learn.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-writefile

invoke WriteFile, eax, buffer_text, buffer_size, bytes_to_write, 0

;https://learn.microsoft.com/en-us/windows/win32/api/processthreadsapi/nf-processthreadsapi-exitprocess

invoke ExitProcess, 0

.end main

Each step is describe in the source code. Run and test with… Read More »

Programming with FASM – OpenAI and FASM programming.

The entire world map praises OpenAI for its ability to analyze, sort, and give correct feedback on a defined issue. I do not completely agree, there are still reminders related to the way of solving complex tasks. An example is creating source code in an assembler for FASM. Although FASM is very strict in terms… Read More »

Programming with FASM – ComboBox Control – part 002.

In the last FASM tutorial I add a simple ComboBox without items. In this tutorial I will add two items and one button to show the output of selected ComboBox. The source code is similar with the source code from the last tutorial. I commented the source code rows for a good image of development… Read More »

Programming with FASM – divide / multiply in Linux – part 009 .

Today I will show you how to use the MMX instructions. SSE stands for Streaming SIMD Extensions and uses 128-bit registers: XMM0 XMM1 XMM2 XMM3 XMM4 XMM5 XMM6 XMM7 The capabilities of the XMM registers are: 2 64-bit floating points (double precision) 2 64-bit integers 4 32-bit floating points (single-precision) 4 32-bit integers 8 16-bit… Read More »

Programming with FASM – read / display character in Linux – part 008 .

I haven’t worked with FASM, Linux, and system functions for a while. Here is an extremely simple example for beginners with output on my nickname: mythcat.

format ELF executable 3
entry start

segment readable executable

BYTES = 255  ;number of byte 255

start:

;read a char from input
char_read:
  mov eax,3
  mov ebx,0  ;0 stdin, 1 stdout, 2 stderr
  mov ecx,char_Buffer
  mov edx,BYTES
  int 0x80

;write byte read to output
char_write:
  mov eax,4
  mov ebx,1
  mov ecx,char_Buffer
  mov dl,[CharRead]
  int 0x80

  jmp char_read

;exit from program
exit:
  mov eax,1  ;  System call 'exit'
  xor ebx,ebx  ;  'xor ebx,ebx' 
  int 0x80

segment readable writeable

  char_Buffer db BYTES dup(0)
  CharRead db 1

format ELF executable 3

entry start

segment readable executable

BYTES = 255 ;number of byte 255

start:

;read a char from input

char_read:

mov eax,3

mov ebx,0 ;0 stdin, 1 stdout, 2 stderr

mov ecx,char_Buffer

mov edx,BYTES

int 0x80

;write byte read to output

char_write:

mov eax,4

mov ebx,1

mov ecx,char_Buffer

mov dl,[CharRead]

int 0x80

jmp char_read

;exit from program

exit:

mov eax,1 ; System call 'exit'

xor ebx,ebx ; 'xor ebx,ebx'

int 0x80

segment readable writeable

char_Buffer db BYTES dup(0)

CharRead db 1

The result is … as follows:

[mythcat@desk fasm]$ ./fasm char_write.asm 
flat assembler  version 1.73.24  (16384 kilobytes memory)
3 passes, 428 bytes.
[mythcat@desk fasm]$ ./char_write 
m
my
yt
th
hc
ca
at
t^C

[mythcat@desk fasm]$ ./fasm char_write.asm

flat assembler version 1.73.24 (16384 kilobytes memory)

3 passes, 428 bytes.

[mythcat@desk fasm]$ ./char_write

t^C

Programming with FASM – the format ELF executable – part 007 .

The tutorial for today is about debugging and FASM with fdbg tool. For debugging and testing you can use any debugger, but you can use the You can here all version for these operating system: GUI for Windows x64, Windows x64, Linux x64 and UEFI x64. I used the Linux x64 version for this tutorial.… Read More »