 <p><em>do i need to include an other lib?</em> - Probably. You need <code>msvcrt.inc</code> and <code>msvcrt.lib</code> for <code>crt__itoa</code>.</p> <p><code>masm32rt.inc</code> is the Swiss Army Knife for such cases. Here is a working example:</p> <pre><code>include c:\masm32\include\masm32rt.inc .DATA fmt db "%s",10,0 num dd 1234567 num_str db 16 dup (?) .CODE main PROC ; with CALL: push 10 push OFFSET num_str push num call crt__itoa add esp, 12 push OFFSET num_str push OFFSET fmt call crt_printf add esp, 8 ; or with INVOKE: invoke crt__itoa, num, OFFSET num_str, 10 invoke crt_printf, OFFSET fmt, OFFSET num_str invoke ExitProcess, 0 main ENDP END main </code></pre> <p>The program does not stop. If you don't call it in an extra command prompt window it will open a window and close it immediately. In <code>Qeditor</code> I suggest to insert a line "Run &amp; Pause" into <code>menus.ini</code>:</p> <pre><code>... &amp;Run Program,"{b}.exe" Run &amp;&amp; Pause,cmd.exe /C"{b}.exe" &amp; pause ... </code></pre> <p>Now you have a new item under "Project".</p>