Compilers how do they work

This will also uncover any syntax errors that are present in your source code and will throw an error to the command line. Finally, if no errors are present, the compiler creates an object file with the machine language binary necessary to run on your machine.

There is a final important step to reach an executable program. In order for you to have a final executable program, another utility known as the linker must combine your object files with the library functions necessary to run the code.

Think of it as having all the necessary blocks to build a house. The compiler made all the blocks but the linker is the one that sticks them all together to finally create a house. Once this is done, you now have a functioning executable file! It is as simple as clicking the build and run buttons, they will create a file in the project folder.

This will now create an object file and automatically link it for you. If you look in that same folder, you will see a hellWorld. The Java programming language does not fit into either the compiled language or interpreted language models. This is illustrated in the figure below.

The Java compiler javac converts the source code into bytecode. Bytecode is a kind of average machine language. This bytecode file. The interpreter is referred to as a Virtual Machine. Thus, Java is an example of a Virtual Machine programming language.

Virtual machine languages were created to be a compromise between compiled and interpreted languages. Under ideal conditions, virtual machine language programs run closer in speed to compiled language programs but have the platform indepency of interpreted language programs. Virtual machine languages makes use of both a compiler and an interpreter. The compiler converts the source code into a kind of average machine language.

In Java, this average machine language is called bytecode. In Visual Studio. To keep the discussion on this page simpler, this compiled code will be referred to generically as bytecode from this point on. The interpreter for virtual machine languages is a special program that provides the runtime libraries for the given operating system.

That means that there is a different virtual machine interpreter for all of the supported operating systems. The way that virtual machine programming languages get some of the speed of compiled languages is that the source code is run through the compiler to create the bytecode. That conversion takes place before the program is ever run.

The way that virtual machine languages gain their portability platform independence is by having a different interpreter for each supported operating system. This interpreter ties in the correct runtime libraries for each different operating system.

The compiled bytecode is an average machine language that will work without changes with any of the virtual machine interpreters for that language. This process is illustrated next. We have a compiler that converts the source code into bytecode. This can be simulated by clicking on the Compile button. Once the bytecode has been created, that same bytecode can be used without any changes on any operating system that has a virtual machine interpreter for the programming language.

Note that each of the virtual machine interpreters have different runtime library code, because each operating system has different runtime libraries. This is how the virtual machine language gets around platform dependency problems. Improve this question. Dynamic Dynamic 5, 9 9 gold badges 42 42 silver badges 73 73 bronze badges.

Too broad, at least the "How does it work" part. There are whole books written on that topic. The question is broad enough that I'd be tempted to give the smart alec response of, "Compilers translate code from one language to another," as that is the general idea that has a lot of nuances within that once one starts to look at what does that really involve. Yes and I think it has been answered pretty well. Any explanation of how a compiler works will either be too broad or too complicated.

It's a complicated subject, and the compilers classes were the hardest computer-related courses I ever took. David Of course compilers are complicated, and you cannot explain all the details of how they work here.

However, I am sure you had a basic high-level understanding of what a compiler is or how it works before you took your compiler course. Show 4 more comments. Active Oldest Votes. Lexing - break up the text of the program into "tokens".

The tokens are the "words" of the programming language, such as identifiers keywords, variable names, function names, etc. Parsing - convert the sequence of tokens into a parse tree, which is a data structure representing various language constructs: type declarations, variable declarations, function definitions, loops, conditionals, expressions, etc. Optimization - evaluate constant expressions, optimize away unused variables or unreachable code, unroll loops if possible, etc.

Translate the parse tree into machine instructions or JVM byte code. Improve this answer. Dima Dima Actually, it transform a language into another. The same goes for Vala compiler. I would argue that C-front was not a compiler but a front-end to the C compiler. Or a stage in the compilation process, if you will.