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Why Learning Assembly Language Is Still Good

Posted by michael on from the atavistic dept.

nickirelan writes "Why Learning Assembly Language Is Still a Good Idea by Randall Hyde -- Randall Hyde makes his case for why learning assembly language is still relevant today. The key, says Randall, is to learn how to efficiently implement an application, and the best implementations are written by those who've mastered assembly language. Randall is the author of Write Great Code (from No Starch Press)."

8 of 667 comments (clear)

  1. Why it's still good... by WilliamsDA · · Score: 5, Interesting

    Also, don't forget, a good deal of programming is still done in assembly. Both in a job I've had coding stuff and in my current research (crypto), I did/do a lot of assembly programming. Yes, learning assembly will make a better programmer out of those who never will code assembly again, but for some people, assembly is a valuable and often-used skill

  2. Schools not teaching assembly anymore by csimpkins · · Score: 5, Interesting

    It's a shame that schools are phasing assembly classes out of their computer science curriculums. If anything, it makes for a great foundation on which to learn more modern languages while teaching students things about computers that they probably wouldn't take the time to learn otherwise.

    1. Re:Schools not teaching assembly anymore by dsheeks · · Score: 5, Interesting

      Knowing something about the low level hardware / machine instructions and what compilers do to translate high level languages definitely helps programmers make better programming decisions.

      Given the rise of byte code environments like Java and .NET and the sophisticated tools available for working with them, I would think schools would do well to teach a class programming at that level. While obviously not a true assembly language, something like Java byte code is a lower level look at how programs really work, and since Java is highly portable you wouldn't have to worry about what hardware the students used like you would with an actual assembly language course. I still think doing some work with assembly and getting some exposure to hardware architectures is best, but this might be a reasonable alternative.

  3. how many people actually program in assembly? by Doppler00 · · Score: 5, Interesting

    I've programmed a few embedded systems in assembly and it's not very fun at all.

    To make matters worse, each CPU has it's own instruction set, and special set of commands that you must learn before you can even sit down and start writing code.

    With C++ or at least a C compiler, you don't need to worry about so many implementation details. You should only resort to assembly if you absolutely, must have the performance required. Maybe the author of this article forgets how difficult it is to debug assembly code, or how difficult it is to implement abstract concepts such as OO at such a low level.

    I don't agree at all that writing "efficient code" necessarily creates better code. Writing "clearer" is better from a quality standard.

    We have compilers for a reason, to produce assembly code as efficiently as possible for a higher level language. Most 99% of the time, the compiler will optomize the code just as well, or better than you can.

    I would still recommend learning assembly language to C++ programmers simply so they understand how the computer is actually working. But to require anyone to program in assembly requires a great deal of justification.

  4. Re:Debugging by Tony-A · · Score: 5, Interesting

    Absolutely.

    Disclaimer: I learned to debug before I learned to code.
    With extremely few exceptions, machine code performs exactly as advertised. When things are not exactly as they should be, it helps to be able to see exactly what is going on.

    Performance is much more a matter of structure (exponential complexity) than language (poor linear complexity). As to level, "high level" languages limit you to their implementation of a few concepts. Depending on where the heavy lifting is, Perl could easily outperform optimized C.

  5. Try the games industry by Jack+Porter · · Score: 5, Interesting

    While the majority of the Unreal engine is C++, we often write assembly-code versions of critical functions for specific platforms. Of course this is done after the C++ versions are tried and tested, and the bottlenecks are idetified.

    To take full advantage of processor features like SSE or AltiVec you don't really have a choice.

    For example, UT2004 contains SSE and AltiVec assembly versions of some of the vector and matrix manipulation functions, some of the visibility culling code, etc. The amount of work Dan Vogel put into this kind of optimization is one of the reasons that UT2004 runs better than UT2003 on the same hardware.

    Learning assembly language is useful, as it's sometimes the right tool for the job.

  6. "Premature optimization is the root of all evil" by richieb · · Score: 5, Interesting
    To quote Donald Knuth.

    Having said that, knowing assembler is useful because it teaches you how the machine works.

    However, most modern compilers can generate code that is much faster than handwritten assembler - especially because they know how to take advantage of the specialized processor architectures (hyper-threading, pipeling etc).

    --
    ...richie - It is a good day to code.
  7. More important to read than write by Diomidis+Spinellis · · Score: 5, Interesting
    It is vastly more important to be able to read assembly code than write it. In most cases this involves reading the code the compiler generates.

    An earlier poster mentioned how such a skill can help you find compiler bugs. This can be the case, but it is rare; I have located two such bugs in 20 years of programming. A more common use is to locate bugs in your code. When your brain refuses to see the missing braces around the wrongly indented code, or an spurious semicolon at the end of an if or while statement, reading the generated assembly code can save some extra hours of frustration. You will be able to see that the code the compiler generates differs from the code you think you wrote, and this will point you to the bug's location.

    As I argue in Code Reading, other cases where reading assembly code can be of use are:

    • to understand how an implementation-defined operation (e.g. a type cast) is actually performed,
    • to see how compiler optimizations affect the resulting code,
    • to verify that hardware-specific code written in C/C++ actually performs the operations you expect, and
    • to learn how a particular construct can be written in symbolic code.

    To read compiler-generated assembly code you need:

    • An understanding of the processor's architecture: registers, instruction format, addressing modes. See for example Intel's Pentium Architecture Manual.
    • A handbook of the processor's instruction set. Again, see for example Intel's Pentium Instruction Set Reference Manual A-M and Intel's Pentium Instruction Set Reference Manual N-Z.
    • An appreciation of how compilers generate code for modern structured languages. The key ideas here are the stack as a way to handle nested function and method calls, the frame pointer as a way to access function arguments and local variables, and the virtual function table often used for implementing dynamic dispatch in OO languages. The Red Dragon Book is the venerable classic here.
    • A way to obtain an assembly code listing of your high-level language code. The Unix compiler's -S switch, and the Java SDK "javap -c" command are two methods I often use. In gdb you can use the disassemble, nexti, and stepi commands to examine your program at the level of discrete processor instructions.

    Obligatory "hello, world" program written in i386 assembly:

    hello: .string "hello, world\n"
    .globl main
    main:
    pushl $13
    pushl $hello
    pushl $1
    call write
    addl $12, %esp
    xorl %eax, %eax
    ret

    Diomidis Spinellis - #include "/dev/tty"