How to write to the console in fasm?

Question

I'm exceptionally new to assembly. I only picked it up yesterday and I've looked through many examples and still can't figure out for myself how to write to the console. I always get an error when I seem to replicate it in my own way.

Trimurti

Answer 1

The easiest way is to use the C functions. In its simplest use, printf() takes a string as a parameter and writes it on the standard output.

This code should work:

format PE console
entry start

include 'win32a.inc'

section '.text' code executable
start:
        push hello
        call [printf]
        pop ecx

        push 0
        call [ExitProcess]

section '.rdata' data readable
        hello db 'Hello world!', 10, 0

section '.idata' data readable import
        library kernel32, 'kernel32.dll', \
                msvcrt,   'msvcrt.dll'
        import kernel32, ExitProcess, 'ExitProcess'
        import msvcrt, printf, 'printf'

Strip

this closes the window immediately :( – Tripp

@Tripp The simplest solution is to keep the command line program open. An alternative is to call getchar() or similar at the end of the program, or create a batch file which calls your program, then uses the pause command. Let me know if you need more information. – Jacquard

how to do it without the include – Roundish

The only code on the internet that actually works, for this purpose. – Doubtless

Answer 2

Use WriteConsole.

include 'win32wxp.inc'

.code
  start:
        invoke  AllocConsole
        invoke  WriteConsole,<invoke GetStdHandle,STD_OUTPUT_HANDLE>,tex,12,dummy,0
        invoke  Sleep,-1
.end start

.data
tex     TCHAR   'Hello World!'
dummy   rd      1  

Materially

If you want to be able to use pipe redirection of your output, you can use WriteFile in a similar manner. – Taxi

how do u do it without the include – Roundish