Is C# partially interpreted or really compiled?

问题:

There is a lot of contradicting information about this. While some say C# is compiled (as it is compiled into IL and then to native code when run), others say it's interpreted as it needs .NET. EN Wiki says:

Many interpreted languages are first compiled to some form of virtual machine code, which is then either interpreted or compiled at runtime to native code.

So I'm quite confused. Could anyone explain this clearly?

回答1:

C# is compiled into IL, by the c# compiler.

This IL is then compiled just-in-time (JIT) as it's needed, into the native assembly language of the host machine. It would be possible to write a .NET runtime that interpreted the IL instead though. Even if this was done, I'd still argue that c# is a compiled language.

回答2:

A purely compiled language has some advantages. Speed, as a rule, and often working set size. A purely interpreted language has some advantages. Flexibility of not needing an explicit compilation stage that allows us to edit in place, and often easier portability.

A jitted language fits in a middle ground in this case.

That's a reason alone why we might think of a jitted language as either compiled or as interpreted depending on which position on which metric we care about attaining, and our prejudices for and against one or the other.

C# can also be compiled on first run, as happens in ASP.NET, which makes it close to interpreted in that case (though it's still compiled to IL and then jitted in this case). Certainly, it has pretty much all the advantages of interpreted in this case (compare with VBScript or JScript used in classic ASP), along with much of the advantages of compiled.

Strictly, no language is jitted, interpretted or compiled qua language. We can NGen C# to native code (though if it does something like dynamically loading an assembly it will still use IL and jitting). We could write an intepretter for C or C++ (several people have done so). In its most common use case though, C# is compiled to IL which is then jitted, which is not quite the classic definition of interpreted nor of compiled.

回答3:

Too many semantics and statements based on opinion.

First off: C# isn't an interpreted language; the CLR and JVM are considered "runtimes" or "middleware", but the same name applies to things like Perl. This creates a lot of confusion among people concerned with names.

The term "Interpreter" referencing a runtime generally means existing code interprets some non-native code. There are two large paradigms: Parsing reads the raw source code and takes logical actions; bytecode execution first compiles the code to a non-native binary representation, which requires much fewer CPU cycles to interpret.

Java originally compiled to bytecode, then went through an interpreter; now, the JVM reads the bytecode and just-in-time compiles it to native code. CIL does the same: The CLR uses just-in-time compilation to native code.

Consider all the combinations of running source code, running bytecode, compiling to native, just-in-time compilation, running source code through a compiler to just-in-time native, and so forth. The semantics of whether a language is compiled or interpreted become meaningless.

As an example: many interpreted languages use just-in-time bytecode compilation. C# compiles to CIL, which JIT compiles to native; by contrast, Perl immediately compiles a script to a bytecode, and then runs this bytecode through an interpreter. You can only run a C# assembly in CIL bytecode format; you can only run a Perl script in raw source code format.

Just-in-time compilers also run a lot of external and internal instrumentation. The runtime tracks the execution of various functions, and then adjusts the code layout to optimize branches and code organization for its particular execution flow. That means JIT code can run faster than native-compiled code (like C++ typically is, or like C# run through IL2CPP), because the JIT adjusts its optimization strategy to the actual execution case of the code as it runs.

Welcome to the world of computer programming. We decided to make it extremely complicated, then attach non-descriptive names to everything. The purpose is to create flamewars over the definition of words which have no practical meaning.

回答4:

Look here: http://msdn.microsoft.com/library/z1zx9t92

Source code written in C# is compiled into an intermediate language (IL) that conforms to the CLI specification.

(...)

When the C# program is executed, the assembly is loaded into the CLR, which might take various actions based on the information in the manifest. Then, if the security requirements are met, the CLR performs just in time (JIT) compilation to convert the IL code to native machine instructions.

回答5:

If you feel, learned, or are old school, that a compiled EXE is going from source to machine code then C# is interpreted. If you think compiled means converting source code into other code such as byte code, then yes its converted. For me, anything that takes run-time processing to work in the OS it was built for is interpreted.

回答6:

First off let's understand the definitions of interpreted and compiled.

"Compile" (when referring to code) means to translate code from one language to another. Typically from human readable source code into machine code that the target processer can... process.

"Interpret" (when referring to code) ALSO means to translate code from one language to another. But this time it's typically used to go from human readable source code into an intermediate code which is taken by a virtual machine which interprets it into machine code.

Just to be clear
Source code -> Compiler -> Machine code
Source code -> Compiler -> Byte Code -> Interpreter -> Machine code

Any language can, in theory, be interpreted or compiled. Typically Java is compiled into bytecode which is interpreted by the Java virtual machine into machine code. C# is typically interpreted into bytecode which is compiled by the CLR, the common language runtime, another virtual machine.

By and far the whole thing is a marketing gimmick. The term "interpreted" was added (or at least, increased in usage) to help showcase how neat just-in-time compiling was. But they could have just used "compiled". The distinction is more a study of the English language and business trends rather than anything of a technical nature.

回答7:

C# is both interpreted and compiled in its lifetime. C# is compiled to a virtual language which is interpreted by a VM.

The confusion stems from the fuzzy concept of a "Compiled Language".

"Compiled Language" is a misnomer, in a sense, because compiled or interpreted is not a property of the language but of the runtime.

e.g. You could write a C interpreter but people usually call it a "Compiled Language", because C implementations compile to machine code, and the language was designed with compilation in mind.

回答8:

I believe this is a pretty old topic.

From my point of view, interpreted code will go through an interpreter, line by line translate and execute at the same time. Like example javascript, it is an interpreted code, when a line of javascript ran into an error, the script will just break.

While compiled code, it will go through a compiler, translate all code to another form of code at once, without execute it first. The execution is in another context.

回答9:

C# is compilable language.

Probbably, I repeat, probbably, as I met too those kind of opinions, the fact that someone thinks that there is an Interpreter for C# language, is due the kind of projects like

C# Interpreter Console

or, for example, famous

LinqPAD

where you can write just lines of the code and execute them, which brings to think that it's Python like language, which is not true. It compiles those lines and executes them, like a ordinary compilable programming language (from workflow point of view).

回答10:

C#, like Java, has a hybrid language processor. Hybrid processors perform the jobs of both interpretation and compilation.

回答11:

Since a computer can only execute binary code, any language will lead to the production of binary code at one point or another. The question is : does the language let you produce a program in binary code? If yes, then it is a compiled language : by definition "compiled" in "compiled language" refers to compilation into binary code, not transformation into some intermediary code. If the language lead to the production of such intermediary code for a program, it will need an additional software to perform the binary compilation from this code : it is then an interpreted language. Is a program "compiled" by C# directly executable on a machine without any other software at all installed on this machine? if no, then it is an interpreted language. For an interpreted language, it is an interpreter that will generate the underlying binary code, most of the time in a dynamic way since this mechanism is the basis of the flexibility of such languages. rem. : sometimes it does not look obvious because the interpreter is bundled into the OS

回答12:

If we agree with the definition of interpreter «In computer science, an interpreter is a computer program that directly executes, i.e. performs, instructions written in a programming or scripting language, without requiring them previously to have been compiled into a machine language program.» there is no doubt: C# is not an interpreted language.

Interpreter on Wikipedia