CODEWITHSUNDEEP
assemblycompilationmasm32-bit16-bit
Roy Kuper
Roy Kuper

Reputation: 127

Diffrences between .IF and CMP? INVOKE and PUSH&CALL? Which one to use?(MASM)

in MASM, you have IF,WHILE,INVOKE and etc. , which in other assemblers like NASM or TASM:

IF=CMP, INVOKE = push parameters and call function , loops(like WHILE) = CMP and JMP to LABELS, and so on....

So I don't understand, If i'm writing IF in MASM, it's tanslated to CMP when I Build the program(assemble&link)? the loops are translated to CMP and JMP to some LABLES? The INVOKE is translated to push parameters and call the function? Basically what Im asking is, if im using IF WHILE INVOKE and so on, They translated to what written here:https://en.wikipedia.org/wiki/X86_instruction_listings or they are compiled like those basic commands.

Because for example, I wrote a simple chat, and this is the socket part:

        invoke socket,AF_INET,SOCK_STREAM,IPPROTO_TCP
        .IF eax==INVALID_SOCKET
            invoke crt_printf,offset Socketerror,offset formatMessagePRINT
            WSAGetLastErrorMACRO
            jmp End_Program
         .else
            mov [ListenSocket],eax
            invoke crt_printf,offset SocketSuccess,offset formatMessagePRINT
        .ENDIF

As you can see, It is look like a code that written in high level programming language. and this is not what I wanted. I want to write programs in assembly in the lowest level that can be written.

So how to write in 32 BIT Assembly in the lowest level that can be written? Do I need to write with the basic commands of 16 bit Assembly (https://en.wikipedia.org/wiki/X86_instruction_listings) and not IF WHILE INVOKE and so on..? this is the only things that I need to stop doing?

Upvotes: 2

Views: 256

Answers (1)

gyc
gyc

Reputation: 4360

If i'm writing IF in MASM, it's tanslated to CMP when I Build the program(assemble&link)?

Yes. For example:

.IF ax==1 
  MOV bx,2 
.ELSE 
  MOV bx,0 
  MOV cx,2 
.ENDIF

Is assembled to:

00401006 CMP AX,1 
0040100A JNZ SHORT 00401012 
0040100C MOV BX,2 
00401010 JMP SHORT 0040101A 
00401012 MOV BX,0 
00401016 MOV CX,2

Those high level constructs are here to help with size and readability when the program becomes complex.

The invoke part is also translated to CALL and PUSH and this macro comes in handy in complex programs like the chat you mentionned.

However, using that high level assembly syntax will make it hard to port the code to another assembler since only MASM uses it.

So how to write in 32 BIT Assembly in the lowest level that can be written?

Just write plain assembly? MASM doesn't force you to use .IF and INVOKE. There are loads of tutorials that explain how to do that.

You can alternatively compile your chat program and decompile it to see what was generated by MASM.

Upvotes: 2

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