**whether the interpretation follows compilation phase during the exection of a pgm?**simply what happens when we run a program?if these are different things then what will perform syntax checking before interpretation.As i read python is a interpreted language then checking of statements done by what?
You have two options:
Compiled languages
Interpreted languages
In a compiled language, you need a compiler that gets source code as input and generates a binary as output that can run on a given target platform. For example, C, C++ or Java are compiled languages. After compiler generates the binary, you execute that binary on the target platform. The main steps involved in the compilation process to generate a binary are lexic, syntactic and semantic analysis, and code generation.
The compiler is a program (binary) that runs on the native platform and generates code for a given target platform. You have two options:
* target_platform == native_platform (native-compiler)
* target_platform != native_platform (cross-compiler).
If you have a x86_64 desktop PC, your compiler runs on x86_64 and generates code that runs on x86_64, your have a native compiler. In this case, the compiler generates native machine code.
If you have a x86_64 desktop PC, your compiler runs on x86_64 and generates code that runs on a different platform (such as JVM), you have a cross-compiler. You should understand that Java language uses a cross-compiler that gets java language as input, and generates byte-code that runs on the JVM (not on the x86_64 machine) as output.
Other cross-compilers such as arm-linux-gcc, mips-linux-gcc, ppc-linux-gcc, and more, get C source code as input and generate binary to run on the proper target platform (ARM, MIPS, PPC).
In an interpreted language, you don't need a compiler to generate code, so a binary is not generated at the end of the process. bash and python are interpreted languages. The interpreter of the language (a binary installed in your PC such as /bin/bash or /usr/bin/python) receives input source code, interprets it, and executes it to generate the output. The steps followed to interpret the source code are exactly the same followed by a compiler, except the interpreter doesn't generate code, just executes it after analyzing.
I wrote an article some time ago explaining how you can write an interpreter of a custom-defined language using python. This article is written in spanish, but the whole process is explained step-by-step, so you can learn a lot if you are interested on it. At the end of the articles you can find the source code to download and test. Source code is available in github. The article is available at this link
Hope it helps! :)
Related
I am diving into the world of COBOL and have written a simple program that compiles and runs as intended from my KDE Plasma command line using open-cobol (cobc). I have seen a few sites mention that COBOL is quite portable and does not require multiple compilations, but when I try to run the same output program on Windows 10 (ie 32-bit), the system states that the program is a 16-bit application and thus cannot run.
Are there parameters that I can use with cobc to compile in such a way that my programs will run on Windows 10, or am I fundamentally misunderstanding the portability of this language?
Compilation command: cobc -x -o program program.cob
Your program is likely already a 64bit executable (depending on your actual OS, otherwise its 32bit), but it is definitely no Windows binary (and because Windows doesn't recognize it, it just guesses this is a 16bit executable).
COBOL itself is portable, even between different compilers (if you restrict yourself to "standard" COBOL or use only the extensions that the compilers used share), but you need "some" native parts in any case.
As a well known example take Java or .NET: the "runtime" is a native binary, which executes the java (or msil) byte code.
There are some COBOL compilers generating intermediate code which is actually portable and can be used with the "native runtime" you have to install beforehand.
The easiest option for your case: take a compatible compiler and recompile your COBOL source for this platform on this platform.
I'd suggesting the successor of OpenCOBOL: GnuCOBOL, using the official windows binaries.
I am a student in Computer Science, and I am learning programming with Pascal.
I have found an interesting Pascal compiler, P4 (http://homepages.cwi.nl/~steven/pascal/).
To know more about Pascal, I am trying to compile their source code, but I failed.
In this web page, they said:
Compile pcom.p and pint.p with a Pascal compiler. You obviously have to have a Pascal compiler already. This gives you a Pascal compiler (pcom) that produces P4 code, and an interpreter (pint) that runs P4 code.
To use the compiler, run pcom with the Pascal program as standard input. This produces any diagnostics on standard output, and its code on a Pascal file that is called prr. Check with your Pascal compiler how this gets assigned to a file in the filestore. You may have to change the lines 'rewrite(prr)' in pcom.p and pint.p and 'reset(prd)' in pint.p for your compiler, for instance to "rewrite(prr, 'prr')" etc.
To run the resulting code, run pint with the prr output produced by pcom as input for the file 'prd', and input for the compiled Pascal program on standard input.
I have compiled it with Free Pascal (on https://ideone.com/), but failed too.
Free Pascal Compiler version 2.6.4+dfsg-4 [2014/10/14] for i386
Copyright (c) 1993-2014 by Florian Klaempfl and others
Target OS: Linux for i386
Compiling pcom.p
pcom.p(1,3) Warning: Unsupported switch "$L"
pcom.p(88,23) Fatal: Syntax error, ":" expected but ")" found
Fatal: Compilation aborted
Error: /usr/bin/ppc386 returned an error exitcode (normal if you did not specify a source file to be compiled)
I don't know how to compile this source code in Windows machine, because I know Pascal language only.
Can I compile it with Turbo Pascal (without any requirement) on Windows XP? Can you remove some part of script for Pascal compiling only?
Free Pascal's Florian has been working getting Scott Moore's P5 compiler (which is a P4 compiler accepting a larger subset of Pascal) to work with FPC's ISO mode for old sources. However it will work (mostly) only in development versions (including the upcoming "stable" branch 3.0.x).
I tried last summer and it compiled and generally worked with FPC 3.x and the -Miso parameter (to select ISO style dialects). IIRC the last thing fixed was ISO style parameter transfer.
I quickly tried the referenced P4 compiler version and it seems to stumble on a few spots with "comment this" comments related to switching back and fro from ISO Mode. If I comment those files, pint compiles. (and then you could run the original bytecode if necessary)
pcom then still stumbles on taking the ord() of a pointer, which is obviously not very portable either, but unfortunately with 20+ occurrences that have to be replaced with ord(ptrint()).
pcom still doesn't compile then, FPC doesn't like passing union fields to VAR parameters. Working around that with a variable and the source compiles, 15 minutes total.
The fixed sourcecode with extra mode statements is at http://www.stack.nl/~marcov/files/p4fixed.zip but requires (as yet unreleased) FPC 3.0 or newer.
The resulting EXE binary can compile the original pcom source to bootstrap itself to bytecode.
You want to get an ISO 7185 compliant compiler to compile that. It is true that Pascal-P4 (the proper name) was written prior to the ISO 7185 standard. However, the adaption to the standard is generally less of a change set than adaption to a dielect.
You will find that work already done and documented at:
http://sourceforge.net/projects/pascalp4/
It specifies use of GPC. However, as Marco said, it is possible with more work to adapt to FPC, and I believe the FPC folks are improving the ISO 7185 capability of their compiler.
Having said that, I'm not sure why Pascal-P4 would be an interesting target. Pascal-P4 was a subset compiler, meaning an incomplete implementation of Pascal. You will find a complete implementation as Pascal-P5:
http://sourceforge.net/projects/pascalp5/
And I believe it has less portability issues as well.
Good luck.
I just Likely know that in which platform operating system coded.
as per my knowledge.
Windows kernel written in C language.
Linux kernel is also written in C language.
but remain operating system in?
In which Platform C language is written?
Yes, the Windows kernel and Linux kernels are written in C. Most operating systems tend to be.
There are operating systems written in other languages though, the Chorus kernel for example is written in C++.
Most C compilers are also written in C. That has the advantage that once you managed to get the compiler running on the machine (generally by compiling it on another machine that already has a working compiler/cross compiler), the machine itself can compile updates to its own compiler without maintaining yet another compiler.
Most parts of the C compiler (like gcc) are written in C themselves. Of course you would need something to bootstrap your compiler such that it can compile itself. That would then be a lower type language like Assembler.
The C language is one of many languages that are considered to be Self Hosting - that is to say that the compiler can compile its own source code, which is written in the same language that the compiler is designed to compile.
You might also want to look into the process of Bootstrapping, which is the process used to get the first compiler for a particular language to run on a given platform - as others have noted, this can be by way of cross-compiling, or by writing the original compiler in a different language, though other techniques are possible.
First off, you might want to improve your question with actual sentences.
Second,
C is not written in a platform, it is written in another programming language.
Most compilers are written in assembler, a somewhat readable version of the actual machine codes sent to the processor.
I don't know if there are other compilers, written in some intermediary language but eventually, everything boils down to assembler code, which compiles to machine code.
This question already has answers here:
Closed 12 years ago.
Possible Duplicates:
How can a language's compiler be written in that language?
implementing a compiler in “itself”
I was looking at Rubinius, a Ruby implementation that compiles to bytecode using a compiler written in Ruby. I cannot get my head around this. How do you write a compiler for a language in the language itself? It seems like it would be just text without anything to compile it into an executable that could then compile the future code written in Ruby. I get confused just typing that sentence. Can anyone help explain this?
To simplify: you first write a compiler for the compiler, in a different language. Then, you compile the compiler, and voila!
So, you need some sort of language which already has a compiler - but since there are many such, you can write the Ruby compiler compiler (!) e.g. in C, which will then compile the Ruby compiler, which can then compile Ruby programs, even further versions of itself.
Of course, the original compilers were written in machine code, compiled compilers for assembly, which in turn compiled compilers for e.g. C or Fortran, which compiled compilers for...pretty much everything. Iterative development in action.
The process is called bootstrapping - possibly named after Baron Munchhausen's story in which he pulled himself out of a swamp by his own bootstraps :)
Regarding the bootstrapping of a compiler it's worth reading about this devilishly clever hack.
http://catb.org/jargon/html/B/back-door.html
I get confused just reading that sentence.
It may help to think of the compiler as a translator, which compilers are often called. Its purpose is to take source code that humans can read and translate it into binary code that computers can read. In the case of Rubinius, the code that it reads happens to be Ruby code, and the code that it converts it into is machine code (actually LLVM machine code which is itself further compiled into Intel machine code, but that's just a background detail). Rubinius itself could have been written in just about any programming language. It just happened to have been written in the same language that it compiles.
Of course, you need something to run Rubinius in the first place, and this most likely a regular Ruby interpreter. Note, however, that once you are able to run Rubinius on an interpreter, you can pass it its own source code, and it will create and run a compiled version of itself. This is called bootstrapping, from the old phrase, "pulling yourself up by the bootstraps".
One final note: Ruby programs can't invoke arbitrary machine code. That part of Rubinius is actually written in C++.
Well it is possible to do it in the following order:
Write a compiler in any language, say C for your Ruby code.
Now that you can compile Ruby code, you can write a compiler that compiles ruby code and compile this compiler with the C compiler you wrote in step 1. wahh this sentence is strange!
From now on you can compile all your ruby code with the compiler written in 2. :)
Have fun! :)
A compiler is just something that transforms source code into an executable. So it doen't matter what it is written in - it can be the same language it is compiling or any other language of sufficient power.
The fun comes when you are writing a compiler for a language for a platform, written in the same language, that doesn't yet have a compiler for your implementation language. Your choices here are to compile on another platform for which you do have a compiler, or write a compiler in another language, and use that to compile the "real" compiler.
It's a 2 step process:
write a Ruby compiler in some other lanaguage like C, assuming a Ruby compiler doesn't yet exist
since you now have a Ruby compiler, you can write a Ruby program that is a (new) Ruby compiler
Since somebody already wrote a Ruby compiler (Matz), you "only" have to do the second part. Easier said than done.
All of the answers so far have explained how to bootstrap the compiler by using a different compiler. However, there is an alternative: compiling the compiler by hand. There's no reason why the compiler has to be executed by a machine, it can just as well be executed by a human.
What does a JIT compiler specifically do as opposed to a non-JIT compiler? Can someone give a succinct and easy to understand description?
A JIT compiler runs after the program has started and compiles the code (usually bytecode or some kind of VM instructions) on the fly (or just-in-time, as it's called) into a form that's usually faster, typically the host CPU's native instruction set. A JIT has access to dynamic runtime information whereas a standard compiler doesn't and can make better optimizations like inlining functions that are used frequently.
This is in contrast to a traditional compiler that compiles all the code to machine language before the program is first run.
To paraphrase, conventional compilers build the whole program as an EXE file BEFORE the first time you run it. For newer style programs, an assembly is generated with pseudocode (p-code). Only AFTER you execute the program on the OS (e.g., by double-clicking on its icon) will the (JIT) compiler kick in and generate machine code (m-code) that the Intel-based processor or whatever will understand.
In the beginning, a compiler was responsible for turning a high-level language (defined as higher level than assembler) into object code (machine instructions), which would then be linked (by a linker) into an executable.
At one point in the evolution of languages, compilers would compile a high-level language into pseudo-code, which would then be interpreted (by an interpreter) to run your program. This eliminated the object code and executables, and allowed these languages to be portable to multiple operating systems and hardware platforms. Pascal (which compiled to P-Code) was one of the first; Java and C# are more recent examples. Eventually the term P-Code was replaced with bytecode, since most of the pseudo-operations are a byte long.
A Just-In-Time (JIT) compiler is a feature of the run-time interpreter, that instead of interpreting bytecode every time a method is invoked, will compile the bytecode into the machine code instructions of the running machine, and then invoke this object code instead. Ideally the efficiency of running object code will overcome the inefficiency of recompiling the program every time it runs.
JIT-Just in time
the word itself says when it's needed (on demand)
Typical scenario:
The source code is completely converted into machine code
JIT scenario:
The source code will be converted into assembly language like structure [for ex IL (intermediate language) for C#, ByteCode for java].
The intermediate code is converted into machine language only when the application needs that is required codes are only converted to machine code.
JIT vs Non-JIT comparison:
In JIT not all the code is converted into machine code first a part
of the code that is necessary will be converted into machine code
then if a method or functionality called is not in machine then that
will be turned into machine code... it reduces burden on the CPU.
As the machine code will be generated on run time....the JIT
compiler will produce machine code that is optimised for running
machine's CPU architecture.
JIT Examples:
In Java JIT is in JVM (Java Virtual Machine)
In C# it is in CLR (Common Language Runtime)
In Android it is in DVM (Dalvik Virtual Machine), or ART (Android RunTime) in newer versions.
As other have mentioned
JIT stands for Just-in-Time which means that code gets compiled when it is needed, not before runtime.
Just to add a point to above discussion JVM maintains a count as of how many time a function is executed. If this count exceeds a predefined limit JIT compiles the code into machine language which can directly be executed by the processor (unlike the normal case in which javac compile the code into bytecode and then java - the interpreter interprets this bytecode line by line converts it into machine code and executes).
Also next time this function is calculated same compiled code is executed again unlike normal interpretation in which the code is interpreted again line by line. This makes execution faster.
JIT compiler only compiles the byte-code to equivalent native code at first execution. Upon every successive execution, the JVM merely uses the already compiled native code to optimize performance.
Without JIT compiler, the JVM interpreter translates the byte-code line-by-line to make it appear as if a native application is being executed.
Source
JIT stands for Just-in-Time which means that code gets compiled when it is needed, not before runtime.
This is beneficial because the compiler can generate code that is optimised for your particular machine. A static compiler, like your average C compiler, will compile all of the code on to executable code on the developer's machine. Hence the compiler will perform optimisations based on some assumptions. It can compile more slowly and do more optimisations because it is not slowing execution of the program for the user.
After the byte code (which is architecture neutral) has been generated by the Java compiler, the execution will be handled by the JVM (in Java). The byte code will be loaded in to JVM by the loader and then each byte instruction is interpreted.
When we need to call a method multiple times, we need to interpret the same code many times and this may take more time than is needed. So we have the JIT (just-in-time) compilers. When the byte has been is loaded in to JVM (its run time), the whole code will be compiled rather than interpreted, thus saving time.
JIT compilers works only during run time, so we do not have any binary output.
A just in time compiler (JIT) is a piece of software which takes receives an non executable input and returns the appropriate machine code to be executed. For example:
Intermediate representation JIT Native machine code for the current CPU architecture
Java bytecode ---> machine code
Javascript (run with V8) ---> machine code
The consequence of this is that for a certain CPU architecture the appropriate JIT compiler must be installed.
Difference compiler, interpreter, and JIT
Although there can be exceptions in general when we want to transform source code into machine code we can use:
Compiler: Takes source code and returns a executable
Interpreter: Executes the program instruction by instruction. It takes an executable segment of the source code and turns that segment into machine instructions. This process is repeated until all source code is transformed into machine instructions and executed.
JIT: Many different implementations of a JIT are possible, however a JIT is usually a combination of a compiler and an interpreter. The JIT first turn intermediary data (e.g. Java bytecode) which it receives into machine language via interpretation. A JIT can often measures when a certain part of the code is executed often and the will compile this part for faster execution.
Just In Time Compiler (JIT) :
It compiles the java bytecodes into machine instructions of that specific CPU.
For example, if we have a loop statement in our java code :
while(i<10){
// ...
a=a+i;
// ...
}
The above loop code runs for 10 times if the value of i is 0.
It is not necessary to compile the bytecode for 10 times again and again as the same instruction is going to execute for 10 times. In that case, it is necessary to compile that code only once and the value can be changed for the required number of times. So, Just In Time (JIT) Compiler keeps track of such statements and methods (as said above before) and compiles such pieces of byte code into machine code for better performance.
Another similar example , is that a search for a pattern using "Regular Expression" in a list of strings/sentences.
JIT Compiler doesn't compile all the code to machine code. It compiles code that have a similar pattern at run time.
See this Oracle documentation on Understand JIT to read more.
You have code that is compliled into some IL (intermediate language). When you run your program, the computer doesn't understand this code. It only understands native code. So the JIT compiler compiles your IL into native code on the fly. It does this at the method level.
I know this is an old thread, but runtime optimization is another important part of JIT compilation that doesn't seemed to be discussed here. Basically, the JIT compiler can monitor the program as it runs to determine ways to improve execution. Then, it can make those changes on the fly - during runtime. Google JIT optimization (javaworld has a pretty good article about it.)
just-in-time (JIT) compilation, (also dynamic translation or run-time compilation), is a way of executing computer code that involves compilation during execution of a program – at run time – rather than prior to execution.
IT compilation is a combination of the two traditional approaches to translation to machine code – ahead-of-time compilation (AOT), and interpretation – and combines some advantages and drawbacks of both. JIT compilation combines the speed of compiled code with the flexibility of interpretation.
Let's consider JIT used in JVM,
For example, the HotSpot JVM JIT compilers generate dynamic optimizations. In other words, they make optimization decisions while the Java application is running and generate high-performing native machine instructions targeted for the underlying system architecture.
When a method is chosen for compilation, the JVM feeds its bytecode to the Just-In-Time compiler (JIT). The JIT needs to understand the semantics and syntax of the bytecode before it can compile the method correctly. To help the JIT compiler analyze the method, its bytecode are first reformulated in an internal representation called trace trees, which resembles machine code more closely than bytecode. Analysis and optimizations are then performed on the trees of the method. At the end, the trees are translated into native code.
A trace tree is a data structure that is used in the runtime compilation of programming code. Trace trees are used in a type of 'just in time compiler' that traces code executing during hotspots and compiles it. Refer this.
Refer :
http://www.oracle.com/webfolder/technetwork/tutorials/obe/java/gc01/index.html
https://en.wikipedia.org/wiki/Just-in-time_compilation
A non-JIT compiler takes source code and transforms it into machine specific byte code at compile time. A JIT compiler takes machine agnostic byte code that was generated at compile time and transforms it into machine specific byte code at run time. The JIT compiler that Java uses is what allows a single binary to run on a multitude of platforms without modification.
Jit stands for just in time compiler
jit is a program that turns java byte code into instruction that can be sent directly to the processor.
Using the java just in time compiler (really a second compiler) at the particular system platform complies the bytecode into particular system code,once the code has been re-compiled by the jit complier ,it will usually run more quickly in the computer.
The just-in-time compiler comes with the virtual machine and is used optionally. It compiles the bytecode into platform-specific executable code that is immediately executed.
20% of the byte code is used 80% of the time. The JIT compiler gets these stats and optimizes this 20% of the byte code to run faster by adding inline methods, removal of unused locks etc and also creating the bytecode specific to that machine. I am quoting from this article, I found it was handy. http://java.dzone.com/articles/just-time-compiler-jit-hotspot
Just In Time compiler also known as JIT compiler is used for
performance improvement in Java. It is enabled by default. It is
compilation done at execution time rather earlier.
Java has popularized the use of JIT compiler by including it in
JVM.
JIT refers to execution engine in few of JVM implementations, one that is faster but requires more memory,is a just-in-time compiler. In this scheme, the bytecodes of a method are compiled to native machine code the first time the method is invoked. The native machine code for the method is then cached, so it can be re-used the next time that same method is invoked.
JVM actually performs compilation steps during runtime for performance reasons. This means that Java doesn't have a clean compile-execution separation. It first does a so called static compilation from Java source code to bytecode. Then this bytecode is passed to the JVM for execution. But executing bytecode is slow so the JVM measures how often the bytecode is run and when it detects a "hotspot" of code that's run very frequently it performs dynamic compilation from bytecode to machinecode of the "hotspot" code (hotspot profiler). So effectively today Java programs are run by machinecode execution.