Hi,
I'm (very) new to assembler.
I'm trying to learning something coding dumb examples with API...


; GetVolumeInformation

format PE GUI 4.0

include '%include%\win32a.inc'

invoke GetVolumeInformation,0,0,0,ddSerial,0,0,0,0
invoke wsprintf,szSerial,fmt,[ddSerial]
invoke MessageBox,0,szSerial,szCaption,MB_ICONQUESTION
invoke ExitProcess,0

ddSerial dd 8
szSerial rb 8
fmt db '%X',0
szCaption db 'GetVolumeInformation',0


[import data removed]

This example retrieve your serial number from hd (where application is running).
I don't know if syntax is right, but this works for me!
The produced output is, for example, 12341234, I'm asking how to insert a "-" sign between 2 numbers (1234-1234).
In C I can use HIWORD and LOWORD, but in asm?
I must use AX and AH instead?
ROL and SHL ?

Thank you for answer.

Just place the following code after wsprintf call:

Thank you,
but it display an X after the serial (1234-1234X)
I think it came from fmt.

You have to increase the size of the buffer to receive the formatted string from 8 to 9 bytes.

Ehm, I change from 8 to 7 'cause from 8 to 9 bytes the outputted string is 1234-1234X%

Sorry, I forgot to tell you how szSerial should be declared:

It (seems) to works

invoke GetVolumeInformation,0,0,0,ddSerial,0,0,0,0
invoke wsprintf,szSerial,fmt,[ddSerial]
mov edx,szSerial+4
mov eax,[edx]
mov [edx+1],eax
mov byte[edx],'-'
invoke MessageBox,0,szSerial,szCaption,MB_ICONQUESTION
invoke ExitProcess,0

ddSerial dd 7
szSerial rb 7
fmt db '%X',0
szCaption db 'GetVolumeInformation',0

Thank you all.

Well, but you should know, that this code overwrites the "%X" string.

Thank you again, I'm new to assembler and I don't understand this F***ING registers very well.

They are not hard to understand. What does my code is:
1. Get last 4 bytes of serial into eax
2. Place them 1 byte upper in memory
3. Place '-' on the 4th position of serial

This means that string should be at least 10 bytes long: 8 bytes serial code, 1 byte '-', 1 byte terminating zero. The problems were because on the place of terminating zero there was beginning of string "%X". When you defined serial buffer 7 bytes long, the position of terminating zero of serial became equal with the position of terminating zero of "%X". That's all.

.. Oh....10 bytes...sorry...

Thanks.