I understand that Parrot is a virtual machine, but I feel like I'm not completely grasping the idea behind it.
As I understand, it's a virtual machine that's being made to handle multiple languages. Is this correct?
What are the advantages of using a virtual machine instead of just an interpreter?
What specifically is Parrot doing that makes it such a big deal?
Parrot is a virtual machine specifically designed to handle several languages, especially the dynamic languages. Despite some of the interesting technology involved, since it can handle more than one language, it will be able to cross language boundaries. For instance, once it can compile Ruby, Perl, and Python, it should be easy to cross those boundaries to let me use a Ruby library in Python, a Perl library from Python, so whatever combination that I like.
Parrot started in the Perl world and many of the people working on it are experienced Perl people. Instead of using the current Perl interpreter, which is showing its age, Parrot allows Perl to have features such as distributable pre-compiled modules (which everyone else has had for a long time) and a smarter garbage collector.
Chris covered the user-facing differences, so I'll cover the other side.
Parrot is register-based rather than stack-based. What that means is that compiler developers can more easily optimize the way in which the registers should be allocated for a given piece of code. In addition, the compilation from Parrot bytecode to machine code can, in theory, be faster than stack-based code since we run register-based systems and have a lot more experience optimizing for them.
Parrot is a bytecode interpreter (possibly with a JIT at a future stage). Think Java and its virtual machine, except that Java is (at the moment) more geared towards static languages, and Parrot is geared towards dynamic languages from the beginning.
Also see Cody's excellent answer! Highly recommended.
Others have given excellent answers, so what remains for me is to explain what "dynamic" languages actually mean.
In the context of a virtual machine it means that the type of a variable is not known at compile time. In "static" languages the type (or at least a parent class of it) is known at compile time, and many optimizations build on that knowledge.
On the other hand in dynamic languages you might know if a variable holds a container type (like an array) or a scalar (string, number, ...), but you have much less type information at compile time.
Another characteristic is that dynamic languages usually make type conversions much easier, for example in perl and javascript if you use a string as a number, it is automatically converted to a number.
Parrot is designed to make such operations easy and fast, and to allow optimizations without knowing having type informations at compile time.
Here is The Official Parrot Wiki.
You can find lots of info and links there.
The bottom of the Parrot wiki home page also displays the latest headlines from the Planet Parrot feed aggregator.
In addition to the VM, the Parrot project is building a very powerful tool chain to make it easier to port existing languages, or develop new one.
The Parrot VM will also provide other languages under-the-covers support for many powerful new Perl 6 features (please see the Official Perl 6 Wiki for more Perl 6 info).
Parrot will provide interoperability between modules of differing languages, so that for example, other languages can take advantage of what will become the huge Perl 6 version of CPAN (the vast Perl 5 module archive, which Perl 6 will be able to access via the forthcoming Perl 5.12).
Honestly, I didn't know it was that big of a deal. It has come a long way, but just isn't seeing much use. The main target language has yet to really arrive, and has lost a huge mind-share among the industry professionals. Meanwhile, other solutions like .Net and projects like Jython show us that the here-and-now can beat out any perceived hype.
Parrot will be what java aimed for but never achieved - a vm for all
OS's and platforms
Parrot will implement the ideas behind the Microsoft's Common Language Runtime for any dynamic language and truly cross-platform
On top of everything Parrot is and will be free and open source
Parrot will become the de facto standard for open source programming with dynamic languages
Related
Do interpreted languages such as Java and Python need an operating system to work?
For example, on a bare-metal ARM microcontroller, can an interpreter be installed such that we can have both compiled code such as C, and interpreted code such as Python working together, Or is an OS needed to support this?
Of course you can write an interpreter that runs on bare-metal, it is just that if the platform does not have an OS any run-time support the language needs must be part of the interpreter. To the extent in some cases that such an interpreter might essentially be an OS. That is if it provides the services to operate a system, it could be called an operating system.
It is not perhaps as simple as interpreted vs compiled. Java for example runs on a virtual machine and is "compiled" to bytecode. The bytecode is interpreted (or just-in-time compiled in some cases), rather then the Java source directly. In an embedded system, it is possible that you would deploy cross-compiled bytecode on the target rather then the source. Certainly however JVMs exist for bare-metal. Some support multi-threading through a third party RTOS, others either have that support built-in or do not support threading at all.
There are interpreters for cut-down subsets of JavaScript and Python that run on bare-metal microcontrollers. I am not sure about full implementations, but it is technically possible given sufficient run-time support even if not explicitly implemented. To fully support some of these languages along with all the standard and third-party libraries and frameworks a developer might expect, may require so much run-time support and resource that it is simpler to deploy and OS, so implementations for resource constrained systems are often subsets or have restricted libraries.
Java needs a VM - virtual machine. It isn't interpreted, but executes byte code. Interpreted would mean grabbing the source in run-time as it goes, like BASIC.
When Java was new and exciting around year 2000, everyone thought it would be the next big general-purpose language, replacing C++. The syntax was so clean, it was "pure OO" and not some "filthy hybrid".
It was the major buzz word of the time. Schools stopped teaching C and C++. MCU manufacturers started to make chips with Java VM in hardware. Microsoft made their own Java "standard". Everyone was high on the Java hype.
Then as the Internet hype as whole collapsed in 2002, it took the Java hype with it. In the sober hang-over afterwards, people started to realize that things like byte code, VMs and garbage collection probably don't belong on bare metal systems.
They went back to using compiled C for hardware-related programming. Or in fact they never stopped, since Java never quite made it there, save for some oddball exotic architectures.
Java remained used only in the areas were it was suitable, namely web, desktop and mobile development. And so it got a second golden age when the smart phone hype struck around 2010.
No. See for example picoJava, which is one of several solutions for running Java natively. You can't get closer to bare metal than running bytecode on the CPU.
No. Some 8-bit computers had interpreted languages in ROM despite not having anything reasonably resembling a modern operating system. The Apple 2 is one example. You could boot the system without any disks or tapes, and it would go straight to a BASIC prompt, where you could write basic (no pun intended) programs.
Note that an operating system is somewhat of a vague term when speaking about these days - these 8-bit computers did have some level of firmware, and this firmware did provide some OS-type functionality like access to basic peripherals. In these days, what we now know as an OS was more commonly called a "DOS" - a Disk Operating System. MS-DOS is one of them, as well as Apple's ProDOS. These DOS's evolved into our modern-day operating systems (e.g. Windows 95 was based on top of MS-DOS, while modern Windows versions derive from a separate branch that was largely re-implemented with more modern techniques), so one could claim that their ancestors are the closest they had to what we now call an OS.
But what is an interpreter but a piece of software?
In a more theoretical sense, an interpreter is simply software - a program that takes input and produces output. Suppose you were to implement a custom solid-state Turing Machine. In this case, your "input" would be the program to be interpreted, and the "output" would be the program's behavior. If "software" can run without an operating system, then an interpreter can.
Is this model a little simplified? Of course. The difference is a matter of degree, not nature. Add very basic user input and output capabilities (e.g. a TTY) and you have the foundation to implement all, or nearly all, of the basic functionality of a language such as Java byte code, Python, or BASIC. The main things you would be missing are libraries and whatnot that depend on things like screen manipulation, multiprocessing, and networking, but you could handle them with time too.
I am going through Scala book by Martin Odersky.
It states that Scala language is highly scalable,reason being that it allows users to add new features which can be utilised as native language support.
It has got me confused with the term 'Scalability'.
I understand that scalability means ability of a software to handle huge amount of data.
So what's the difference here?
In the context of Scala, Odersky usually means that it is scalable in the sense that it can be used for a wide range of tasks, from simple scripting to large libraries to behemoth enterprise applications.
It's good for scripting because of its type inference, relatively low verbosity (compared to Java), and functional style (which generally lends itself to more concise code).
It's good for medium size applications and libraries because of its powerful type system, which means it is possible to write code that mostly or only produces errors at compile time rather than runtime (to the extent that is possible). The Play! framework in particular is founded on this philosophy. Furthermore, Scala runs on the JVM and therefore can harness any of the many, many Java libraries out there.
And it's good for enterprise software because it compiles to JVM bytecode, which already has a great track record in enterprise software; further, the fact that it's statically typed makes the maintenance of very large codebases much easier.
Scala is also applicable to a number of other areas, making it even more "scalable": concurrency/parallelism and domain-specific languages come to mind.
Here is a presentation by Odersky, if you start at slide 6 and go forward, you'll see him explain some other uses of Scala as well.
I've had an eye on Parrot for a little while. I understand that it's a virtual machine designed to run a variety of dynamic languages, and to allow a degree of interoperability (e.g. calling a Perl function from a Python script). So, my question is in two parts:
Is Parrot ready for general use? I can see releases are being made, but it's not obvious whether it's something that works well now, or still a work in progress.
Is there any documentation on how to use Parrot? I've looked at links in previous questions, but all the documentation I can find talks about the various levels of Parrot-specific code (PIR, PASM, etc.), or how to add support for more languages. That's great, but how do I run code in existing languages on Parrot? And how do I use code written in another language?
Finally, I don't want to start a flamewar, but I know Parrot is tied up with Perl 6. I prefer Python. I understand Python is a supported language, but realistically, is it perceived as a multi-language VM, or is it a Perl 6 interpreter with other languages included as curiosities?
I'm a Python developer primarily, so I'm biased. But probably in the same direction as you.
Parrot is intended to be a multi-language VM. Its Perl roots show sometimes ("0" is false, the bootstrapping language NQP is a subset of perl), but at the runtime level it's quite language-agnostic.
That said, interop between languages won't be entirely seamless. For example, the String type will most likely be used as a base by all languages, but a Ruby object will probably need wrappers (but not proxies) to act pythonic. There's no story for object interop, at least not so far.
The Python 3 compiler "Pynie" has quite a way to go. Here's the repo http://bitbucket.org/allison/pynie. Maybe you'd like to help out? Right now it's quite young, not even objects yet.
And to answer your actual question:
Sort of. It's not fast and the languages that target it aren't complete, but it won't crash or corrupt your memory.
Normally, you write code in your favourite High Level Language (Python) and compile your .py code to parrot (and from there, you can compile it to native code if you want to). Another dev can write their Perl(6) code and compile it to parrot and, if the compilers have been written with interop in mind, you'll be able to call a Perl function from python
It is still work in progress, but it's mature enough for language implementors and library developers. Caveat: some subsystems are getting reworked (garbage collection, embedding), so there might be some bumps on the road ahead.
Each language needs a compiler that generates code Parrot understands. These compilers are released separately. (see http://trac.parrot.org/parrot/wiki/Languages )
Most languages targeting Parrot are in an early incomplete state, so interoperability isn't a big issue right now. Parrot isn't a Perl 6 interpreter, but Rakudo Perl 6 happens to be one of the most heavily developed compiler that targets Parrot.
Guess no new project is implemented in languages like Modula, Ada , Oberon .. anymore (right?). But still there are legacy systems floating around, popping out here and there looking for their creators. They cant find them because they might be retired sitting at a beach somewhere enjoying themselves.
Serious:
1) I am wondering if there are still active (experienced) Modula programmers around ?
2) Anyone experience with porting Modula code to a new hardware generation ?
3) Does anyone know about a tool that can re-engineer, means map Procedures and Mod-files in a graphical way. These tools are available for eg. C programs.
Sure, Modula Syntax is not that breathtaking in comparison to todays .net and Java API's with 1000's of methods, but if someone drop about 100.000 lines of almost undocumented sourcode at you (nicely mixed with some 8000 lines assembler), you better know if you better reject it. I have this request and I am very resistant. (Option: port and keep modula source or migrate to other language in 9 months!)
cheers
1) I am wondering if there are still active (experienced) Modula programmers around ?
There are plenty of them, but you have to do a bit of web search to find them. If you search for "Curriculum Vitae" (or "Resume") and "Modula-2" there should be plenty of hits. Also, anybody who has experience in Oberon, Pascal or Delphi will be able to handle Modula-2.
Also there are active Modula-2 projects, most notably:
GNU Modula-2 at http://www.nongnu.org/gm2
Modula-2 R10 at http://modula-2.net/m2r10
Modula2JCC at http://code.google.com/p/modula2jcc
Modulipse at http://modulipse.sourceforge.net
Schwarzer Kaffee http://sourceforge.net/projects/schwarzerkaffee
2) Anyone experience with porting Modula code to a new hardware generation ?
Ask on the GNU Modula-2 mailing list. Many GNU Modula-2 users have Modula-2 code from 16-bit DOS systems they like to port to modern platforms. The GNU Modula-2 website lists this as one important motivation for GM2. The GM2 mailing list is at:
http://lists.nongnu.org/mailman/listinfo/gm2
There is also the Modula-2 Usenet news group, you can reach it via the Google interface at
http://groups.google.com/group/comp.lang.modula2
Last but not least, there is a Modula-2 IRC channel at Freenode
irc://irc.freenode.net/#modula-2
3) How to assess 100.000 lines of Modula-2 source code
"if someone drop about 100.000 lines of almost undocumented sourcode at you (nicely mixed with some 8000 lines assembler), you better know if you better reject it. I have this request and I am very resistant. (Option: port and keep modula source or migrate to other language in 9 months!)"
You may want to contact Rick Sutcliffe, a well known Modula-2 scholar and book author who is also the maintainer of the Modula-2 FAQ in which he states that he does get hired to do consulting work for assessing Modula-2 source code in company take-over situations. It seems to me that your situation might be similar enough to justify hiring an expert to establish the value of the software that is offered to you.
The Modula-2 FAQ is at http://faq.modula2.net
1) I am wondering if there are still active (experienced) Modula programmers around ?
Yes, I'm one. But I already have a job :-)
2) Anyone experience with porting Modula code to a new hardware generation ?
Not clear if you meant porting code or porting a compiler. Porting Wirth's Modula-2 compiler (or Oberon compiler) should be easy. Ada and Modula-3 are another story.
3) Does anyone know about a tool that can re-engineer, means map Procedures and Mod-files in a graphical way. These tools are available for eg. C programs.
I don't understand the question. If you are looking to visualize the import graph of a Modula-2 program, you could easily write something to emit dot. Visualizing call graphs is another story.
Here's my bottom line on Modula-2 and Oberon:
Any C programmer worth his or her salt can quickly learn enough Modula-2 to maintain a large legacy application. Oberon's another story; its model of exported names and type extension is not like the object models found in other OO languages.
Wirth's genius as a language designer was to make things easy for the person writing the compiler. So if you need tools, any good compiler writer can produce them. Wirth's compiler should be available and easy to port.
Ada does not deserve to be mentioned in the same breath with Modula-2 and Oberon.
Ada is still an very active language. I use it in my own research since 1995 and in my lectures since last year at a university.
I myself don't know much of Modula, however I worked at a research center in Brazil that had a packet switching network project (Compac) that was entirely created in Modula-2. If I'm not mistaken they even developed the compiler/linker themselves. Since I don't feel at liberty to point you to specific persons, I would suggest you do a google search for "compac" and "cpqd" and I can pretty much guarantee you will find names of people involved in it. It should come as no surprise that references to it are quite old, from late 80's.
Modula-2 is architecturally not that dissimilar to C. A programmer familiar with C should have little trouble figuring out Modula-2. Given that your application has a significant body of assembler code then you will need someone with low-level skills anyway.
IIRC Modula-2's grammar is LL(1) or nearly so, so writing a parser to generate call graphs for a Modula-2 code base is not beyond the wit of man. Graphviz is your friend if you want a quick and easy way of visualising the call graphs. Again, this suggests that you're up for employing a 'real programmer' to do the porting work.
If you need a reasonably viable Modula-2 compiler, you could look at the Amsterdam Compiler Kit which does have a competent Modula-2 compiler that can target a wide variety of platforms, although it doesn't support Win32 IIRC.
I would suggest that documenting and porting the existing Modula-2 code base is probably easier than attempting to re-write it in C. However, if you need to move to a different processor architecture then you will have to re-write the assembly language bits anyway. This does rather change the value proposition of porting.
If it is you doing the porting then you might consider doing it in two steps.
Arrange with the customer to do a utility to generate the call graph and give them a feasibility study recommending what to do and some estimate of the scope.
Do the port, either porting the code base or re-writing it. Bear in mind that you may not need a low level language for the entire code base if you're running it on a modern computer. You may be able to do it in a mixture of (say) Python and C with less effort than would have been needed for a rewrite purely in C.
Yup.
I realise that you asked this question quite some time ago but I also know that projects that nobody like to handle get kind of delayed...
I built several large systems in Modula-2 over a span of ten years and have this insane habit of taking on impossible tasks.
I have not touched it for about ten years but am absolutely certain that I can port your system for you to almost any other platform. Why not get in touch with me if you are still interested?
Oh yeah - better still, we are both in Singapore :-)
ADW Modula-2 has now been released as freeware. http://www.modula2.org/adwm2/ Since it's free and supports 32 & 64-bit Windows applications (and I know Modula-2), I've picked it up and am using it for small utility work that I want to be a 64-bit Windows binary (most of my work is in Java and .Net, which are fine but sometimes a pure binary is best. I use MASM32 for 32-bit binary Windows apps already).
edit
There's also a project in the works (still very early on, not yet usable as of the date of this edit) now to compile Modula-2 on the JVM (with a transpile to Java option). https://github.com/m2sf/m2j
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I am planning to develop an operating system for the x86 architecture.
What options of programming languages do I have?
What types of compilers are there available, preferably on a Windows environment?
Are there any good sources that will help me learn more about operating system development?
Is it better to test my operating system on a Virtual Machine or on physical hardware?
Any suggestions?
For my final year project in collage I developed a small x86 OS with a virtual memory manager, a virtual file system and fully preemptive multitasking. I made it open source and the code is heavily commented, check out its source forge page at:
https://github.com/stephenfewer/NoNameOS
From my experience I can recommend the following:
You will need x86 assembly language for various parts, this in unavoidable, but can be kept to a minimum. Fairly quickly you will get running C code, which is a proven choice for OS development. Once you have some sort of memory manager available you can go into C++ if you like (you need some kind of memory manager for things like new and delete).
No matter what language you choose you will still need assembly & C to bring a system from boot where the BIOS leaves you into any useable form.
Ultimately, the primary language you choose will depend on the type of OS you want to develop.
My development environment was the Windows port of the GNU development tools DJGPP along with the NASM assembler. For my IDE I used IBM's Eclipse with the CDT plugin which provides a C/C++ development environment within Eclipse.
For testing I recommend BOCHS, an open source x86 PC emulator. It lets you boot up your OS quickly which is great for testing and can be integrated into eclipse so you can build and run your OS at the push of a button. I would also recommend using both VMWare and a physical PC occasionally as you can pick up on some subtle bugs that way.
P.S. OS development is really fun but is very intensive, mine took the best part of 12 months. My advice is to plan well and your design is key! enjoy :)
Language and compiler depend entirely on what you're attempting to accomplish. I would suggest, though, that you might be approaching the problem from too low a level.
There are materials out there on operating system fundamentals. MIT has OpenCourseware on the subject. Read through Andrew Tannenbaum's Operating Systems series, and look at things like Minix.
Get an idea for what's out there. Start tinkering with things. Borrow ideas, and see where they go. You can reinvent the wheel if you really want, but you'll learn more by building on the works of others.
It doesn't really matter, what language you choose. If the language is Turing-complete, then you can write an OS in it.
However, the expressiveness of the language will make certain kinds of designs very easy or very hard to implement. For example, the "liveliness" and dynamism of the old Smalltalk OSs depends on the fact that they are implemented in Smalltalk. You could do that in C, too, but it would probably be so hard that you wouldn't even think about it. JavaScript or Ruby OTOH would probably be a great fit.
Microsoft Research's Singularity is another example. It simply couldn't be implemented in anything other than Sing#, Spec# and C# (or similar languages), because so much of the architecture is dependent on the static type safety and static verifiability of those languages.
One thing to keep in mind: the design space for OSs implemented in C is pretty much fully explored. There's literally thousands of them. In other languages, however, you might actually discover something that nobody has discovered before! There's only about a dozen or so OSs written in Java, about half a dozen in C#, something on the order of two OSs in Haskell, only one in Python and none in Ruby or JavaScript.
Try writing an OS in Erlang or Io, and see how that influences your thinking about Operating Systems!
There is an OS course offered at the University of Maryland that utilizes GeekOS. This is a small, extensively commented OS designed for educational purposes which can be run using the Bochs or QEMU emulators.
For an example of how it is used in a course, check out a previous offering of the course at the class webpage. There, you will find assignments where you have to add different functionality to GeekOS.
Its a great way to get familiar with a small and simple OS that runs on the x86 architecture.
You might want to look up XINU. it's a tiny OS for x86 that isn't really used for anything other than to be dissected by students.
Use ANSI C, and start off with an emulator.
When you port over to a real machine, there will be some assembler code. Context switching and interrupt handling (for instance) is easier to write in assembler.
Andy Tannenbaum has written a good book on OS. Many other good ones exist.
Good luck! There is nothing quite like haveing written your own OS, however small.
Also check out the OSDev.org which have all information you need to get started.
I've done that once for a 386SX, which was on a PCI board. A good source on how to start a X86 cpu in protected mode is the source code of linux. It's just a few assembly statements. After that you can use gcc to compile your C code. The result is objectcode in ELF format. I wrote my own linker, to make a program out of the objectcode. And yes, it worked! Good luck.
Be sure to check out the answers to my question:
How to get started in operating system development
Without a doubt, I'd use Ada. It's the best general-purpose systems-programming language I have come across, bar none. One example, Ada's much better for specifying bit layout of objects in a record than C. Ada also supports overlaying records on specific memory locations. C requires you to play with pointers to acheive the same effect. That works, but is more error-prone. Ada also has language support for interrupts.
Another: Safety. Ada defaults to bound checking array assignments, but allows you to turn it off when you need it. C "defaults" to no bound checking on arrays,so you have to do it yourself manually whenever you want it. Time has shown that this is not the right default. You will forget one where it is needed. Buffer overflow exploits are the single most common security flaw used by crackers. They have whole websites explainng how to find and use them.
As for learning about doing this, the two books I'm aware of are XINU (Unix backwards, nothing to do with Scientology), and Project Oberon. The first was used in my Operating Systems graduate course, and the second was written by Nikalus Wirth, creator of Pascal.
If you are making a full OS, you will need to use a range of languages. I would expect Assembly, C and C++ at the very least.
I would use a Virtual Machine for most of the testing.
C most probably...all major OS-es have been written in C/C++ or Objective-C(Apple)
If you want write an OS then you need a couple of people. A OS can not write a single people. I think it is better to work on existing OS projects
Reactos --> C, Assembler
SharpOS --> C#
JNode --> Java
This is only a short list of OS projects. How you can see there is a project for every possible language.