Decimal value in masm32

Question

I have a problem with one thing in assembly. I create a variable points db 65. The starting value is 65, but when I want to show this value in program using

invoke CreateWindowEx,0,ADDR classStatic,ADDR points, WS_CHILD or WS_VISIBLE,100,100,50,50,hWnd,0,hInstance,0

it returns ASCII. In this example, the character "A". How do I fix it to show "65"?

Answer 1

The CreateWindowEx function is expecting a C-style string, which is a pointer to a NUL-terminated sequence of characters.

What you have passed it is actually invalid input, and I'm rather surprised that you got "A" instead of "A$^a!bunch?*of-@(nasty^&+garbage{%". You got lucky that a 0 was placed after your points constant, probably because of padding inserted by the assembler.

If you want to display a number as the caption of your window, then you will first need to convert that number into a string. There are various ways of doing this. The simplest is just to call a function that will do it for you. Since you're already linking to the Win32 API, you can get away with calling wsprintf. Better yet, link to a C runtime library and call snprintf. Alternatively, you can write your own code that converts a number to a string.

Assuming that your string is static, an even better approach would be to simply use a string in the first place:

points db "65",0

(might want to pick a better name than points).

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Also note that Windows is a Unicode-based operating system, and it implements Unicode via a 2-byte UTF-16 type. Therefore, you should always explicitly call the W-suffixed versions of Windows API functions (or define the UNICODE and _UNICODE symbols), and your string characters will need to be WORD-sized. Therefore, the code would be:

strCaption  dw '6','5',0

invoke CreateWindowExW,0,ADDR classStatic,ADDR strCaption, WS_CHILD or WS_VISIBLE,100,100,50,50,hWnd,0,hInstance,0