Assembly

This is a discussion on Assembly within the Game Programming forums, part of the General Programming Boards category; When you say that it is faster to program in Assembly do you mean it is faster to make or ...

  1. #16
    CAP
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    When you say that it is faster to program in Assembly do you mean it is faster to make or it runs faster because of how it is set up.
    -Microsofts Visual C++ Introductory Kit-
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  2. #17
    Fingerstyle Guitarist taylorguitarman's Avatar
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    Obviously you haven't read the threads closely. Here's a small assembly program from one of my classes. It takes more time to program in assembly but the speed of the program itself can be reduced if done properly.
    Code:
    ;;Program that prompts for user to enter two signed numbers.  Prompts user to
    ;;select and operation to do to the numbers Add, subtract, multiply or divide
    ;;Calculates and displays the result of the selected option
    
    INCLUDE   PCMAC.INC
              .MODEL    SMALL
    
              .STACK    100h
                      
    CR        EQU       13    
    LF        EQU       10   
    ENDSTR    EQU       '$'
    
              .DATA
    Msg1      DB        'Enter the first number: ', ENDSTR
    Msg2      DB        'Enter the second number: ', ENDSTR
    Msg3      DB        'Do you want to add, subtract, multiply or divide?', ENDSTR
    Msg4      DB        '(Enter A,S,M or D): ', ENDSTR
    Msg5      DB        'The Product is: ', ENDSTR
    Msg6      DB        'The Sum is: ', ENDSTR
    Msg7      DB        'The Difference is: ', ENDSTR
    Msg8      DB        'The Dividend is: ', ENDSTR
    Msg9      DB        'The Remainder is: ', ENDSTR
    NUM1      DW        ?      ;;variable that holds the first number
    NUM2      DW        ?      ;;variable that holds the second number
    CHOICE    DB        ?      ;;holds user's choice
    REMAIN    DW        ?      ;;holds the remainder from division
    
              .CODE
              EXTRN     GetDec : NEAR, PutDec : NEAR
    A5        PROC
              mov       ax, @DATA
              mov       ds, ax
                         
              _PutStr   Msg1       ;;displays prompt to get first number
              call      GetDec
              mov       Num1, ax   ;;saves first number as NUM1
    
              _PutStr   Msg2       ;;displays prompt to get second number
              call      GetDec
              mov       Num2, ax   ;;saves second number as NUM2
              mov       bx, NUM2   ;;puts NUM2 into bx for arthimetic for entire program
              _PutCh    LF
    
              _PutStr   Msg3          ;;Prompts user to enter their selection
              _PutStr   Msg4          ;;  A, S, M or D
              _GetCh    Echo
              mov       CHOICE, al    ;;saves user's choice as CHOICE
              _PutCh    LF, LF, CR
    
              mov       al, CHOICE
              cmp       al, 53h      ;;compares CHOICE for subtraction option
              je        SUBTRACT
              cmp       al, 41h      ;;compares CHOICE for addition option
              je        ADDIT
              cmp       al, 4Dh      ;;compares CHOICE for multiplication option
              je        MULTIPLY
                    ;;falls through to division if no jump
    
    ;;---------------------Division Option-----------------------------
              _PutStr   Msg8          ;;outputs string to display quotient
              mov       ax, NUM1
              cwd
              idiv      bx            ;;divides NUM1 by NUM2
              mov       REMAIN, dx    ;;saves remainder in REMAIN
              call      PutDec        ;;displays quotient
              _PutCh    LF, CR
              _PutStr   Msg9          ;;outputs string to display remainder
              mov       ax, REMAIN
              call      PutDec        ;;displays remainder
              jmp       DONE          ;;jumps to end of program
    
    ;;---------------------Addition Option------------------------------
    ADDIT:    _PutStr   Msg6           ;;outputs string to display sum
              mov       ax, NUM1
              add       ax,bx         ;;adds NUM2 to NUM1
              call      PutDec        ;;outputs sum
              jmp       DONE          ;;jumps to end of program
    
    ;;-------------------------Subtraction Option-----------------------
    SUBTRACT: _PutStr   Msg7      ;;outputs string to display difference
              mov       ax, NUM1
              sub       ax, bx    ;;subtracts NUM2 from NUM1
              call      PutDec    ;;outputs difference
              jmp       DONE      ;;jumps to end of program
    
    ;;----------------------------Multiplication Option-----------------
    MULTIPLY: _PutStr   Msg5      ;;outputs string to display product
              mov       ax, NUM1
              imul      bx        ;;multiplies NUM1 by NUM2
              call      PutDec    ;;outputs product
    
    DONE:     _EXIT     0     
    A5        ENDP
              END       A5
    If a tree falls in the forest, and no one is around to see it, do the other trees make fun of it?

  3. #18
    . Driveway's Avatar
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    Wow, I've never seen assembly and I understood most of that. Yes I know there were comments, but I didn't actually read them. Who does?

  4. #19
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    Assembly Language and machine code are two (2) different things. Assembly is a language, just like 'C' is a language. It is a higher-level representation of machine code. C is a higher-level representation of Assembly.

    Assembly is the language you write code in, when working with an Assembler. It allows you to have labels, to name functions, to access API functions via name, and to have variables by names, rather than RAM offsets.

    'Machine' code is the object itself. Actual binary. If you were to see a hex coredump-- you'd be looking at machine code. Nobody writes in machine code (like maybe 1% of the folks on _old_ systems might still have to do it for DoD and governmental projects for bootstrap loaders, or such).

    The reason game programmers use more assembly than the average programmer, is because in games, cycle times count-- you want to get every erg of energy out of the processor, and the most effecient way to do that is to use assembly judiciously to improve frame rates.

    No compiler can currently beat an expert professional assembly programmer at optimization. A compiler has _no idea_ what the programmer is trying to do-- it just pulls snippets in from libraries and binds them together. So a compiler's code tends to be slightly generic by nature.

    ---

    I recommend that all C/C++ programmers try to learn enough assembly that they can write stubs or snippets as necessary. Not only will this dramatically improve your ability to debug your higher-level code, but it will also open your eyes to many things about how a computer works, how your software runs, how the O/S works--- all things that a professional programmer learns.

    ---

    Understanding how things work, lets you overcome seemingly otherwise insurmountable obstacles. For example, let's say you created an interrupt to a callback function. But while in that callback function, you can't access your global variables or created variables at all, and yet you need to allocate variables so that you can do the work)-- how could you do this?

    If it were me, I would take the queue element structure, an O/S structure, resize it by 32-bits, and store the pointer to a RAMblock in those newly acquired bytes. The RAMblock would be a structure containing enough space for my callback's variables. Then I'd set the rest of the interrupt up and be on my way.

    Then when the interrupt fired and the callback got called, I could use a little assembly language on entry to my callback to recover the address of the queue element structure that my interrupt process hangs off of. I could then reclaim that pointer, and be able to access variables from within my callback.

    what can I say, I live this stuff everyday.

  5. #20
    CAP
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    Well

    Seeing as how I am currently just trying to start learning C I took 1 look at that code in Assebly then at the clock and realized I had been staring for quite some time...

    Anyways that was quite possibly the most confusing thing I have ever seen(sorry to say).
    This gave me another question though, you said that if you can program in C and C++ then you should learn enough assebly to make snippets of code. Then how do you insert or use these "snippets"?
    Do you simply insert them like say a library or what??
    -Microsofts Visual C++ Introductory Kit-
    Current Projects: Learning Everything C.

    Everyone has a photographic memory, some people just don't have any film.
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  6. #21
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    The actual insertion depends on the compiler, however most of them will use an
    Code:
    asm{
             //assembly here}
    //or
    
    _asm{
             //assembly here}
    
    //or
    
    __asm{
             //assembly here}

  7. #22
    CAP
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    Ok so you just basically put them in as you would javascript in HTML, that is seems simple enough as soon as I learn more about C's language and grammar(man I thought programming with one language would be hard, what about putting in like 3 or 4 others, I guess I am going to be doing a lot of reading )
    -Microsofts Visual C++ Introductory Kit-
    Current Projects: Learning Everything C.

    Everyone has a photographic memory, some people just don't have any film.
    ______________________________

    When was the last time you went for a colon cleansing? Because quite frankly, you're so backed up with crap that it's spilling out your mouth

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