Assembly

Help:sum two number in asm with API

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Join Date: Aug 2009

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DarkC0de

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Re: Help:sum two number in asm with API

#11

Aug 11th, 2009

thanks it's work now

if you please explain The structure of the code

mov byte ptr num[ eax ], 0

Last edited by DarkC0de; Aug 11th, 2009 at 10:05 pm.

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Join Date: Jun 2009

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wildgoose

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Re: Help:sum two number in asm with API

#12

Aug 11th, 2009

First I have a question. Did your instructor tell you to use the API that comes with masm32 or do it yourself?

mov byte ptr num[eax],0

Memory access can be direct from memory

 Help with Code Tags 
 Assembly Syntax (Toggle Plain Text) 
mov num,al     ; 8-bit
mov num,ax   ;16-bit
mov num,eax   ; 32-bit
mov num,rax   ; 64-bit
 
memory can use a register offset
mov num[ebx],ax        num+value in ebx is new memory location
mov num[ebx*4],ax    num+(value *4)   You can use a scalar
 
In your particular case
mov num[ eax ],0    <-- undefined
0 is an undertermined size so it needs a data type pointer
    byte ptr                byte index
    word ptr               word index
    dword ptr              dword index
    qword ptr              qword index
    oword ptr              oword index 
so...
mov byte ptr num[ eax ],0
...store a zero as a byte at location num+eax
mov num,al     ; 8-bit
mov num,ax   ;16-bit
mov num,eax   ; 32-bit
mov num,rax   ; 64-bit

memory can use a register offset
mov num[ebx],ax        num+value in ebx is new memory location
mov num[ebx*4],ax    num+(value *4)   You can use a scalar

In your particular case
mov num[ eax ],0    <-- undefined
0 is an undertermined size so it needs a data type pointer
    byte ptr                byte index
    word ptr               word index
    dword ptr              dword index
    qword ptr              qword index
    oword ptr              oword index 
so...
mov byte ptr num[ eax ],0
...store a zero as a byte at location num+eax

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Join Date: Aug 2009

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DarkC0de

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Re: Help:sum two number in asm with API

#13

Aug 12th, 2009

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Did your instructor tell you to use the API that comes with masm32 or do it yourself?

i didn't studied Assembly but I hear about assembly and I want to learn the assembly .I ask another forum how i can start with assembly they tell me to start with use API

I'm interested in system and virus protected
and I'm programmer c++,for that I want to learn Assembly

thanks for help me

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wildgoose

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Re: Help:sum two number in asm with API

#14

Aug 12th, 2009

Find a good book and start working the sample problems. You need to work your way up.
Having the ability to single step your code is best!
Since you have C++ how about starting with inline code!

I prefer an assembly file, but inline is much easier to work with initially!

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wildgoose

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Re: Help:sum two number in asm with API

#15

Aug 12th, 2009

There is an author I like that has two books about assembly language.
One is a more advanced book, "Vector Game Math Processors" which I really like. It came with a CD and is out of print but is still available from Amazon.
The other is very complete, is still in print "32/64-Bit 80x86 Assembly Language Architecture" and has downloadable code samples. It has mistakes as I understand the author was rushed but I still like the book.
The files download link...
http://www.jbpub.com/catalog/9781598220025/samples/
The samples are C code that has some inline but has external assembly files that it links with. The best of both worlds. Do your input/output in a higher level language such as C/C++ and call the assembly code directly to do the low level functions.

In your particular case, pick one, compile it and then run it. Set a breakpoint and then single-step following the code into the assembly function. You can use it as a testbench for learning your assembly. The single-stepping with disassembly view and register views turned on will allow you to see the registers and flags changing as the instructions are executed!