The Programming Process

computers do no understand human languages. In fact, at the lowest level, computers only recognize sequences of numbers that represent operational password (op codes because that short). ~ above the other hand, it would be very difficult for human beings to compose programs in regards to op codes. Therefore, programming language were designed to make it simpler for humans to write computer programs.

Programming languages space for humans to read and understand. The regimen (source code) must be translated into machine language so that the computer system can execute the routine (as the computer system only understands an equipment language). The means that this translate in occurs counts on whether the programming language is a compiled language or an interpreted language.

Compiled language (e.g. C, C++)

The following illustrates the programming process for a compiled programming language.


A compiler bring away the program code (source code) and also converts the source code come a maker language module (called things file). Another committed program, referred to as a linker, combines this object file with other previously compiled object records (in details run-time modules) to produce an executable file. This process is diagrammed below. Click initial build to watch an animation of exactly how the executable is created. Click Run executable to simulate the to run of an already created executable file. Click Rebuild to simulate rebuilding of the executable file.

You are watching: A program that combines object files into an executable program is called a


executable document Initial construct Run executable Rebuild
So, for a compiled language the counter from resource code to an equipment executable password takes place before the program is run. This is a an extremely different procedure from what takes ar for an construed programming language.

This is somewhat simplified as many modern programs the are developed using compiled languages renders use of dynamic attached libraries or mutual libraries. Therefore, the executable record may require these dynamic linked libraries (Windows) or shared libraries (Linux, Unix) come run.

Interpreted programming languages (e.g. Python, Perl)

The procedure is different for an construed language. Rather of translating the source code into machine language prior to the executable document is created, one interpreter counter the source code into machine language in ~ the exact same time the regimen runs. This is portrayed below:


construed languages usage a special program referred to as an interpreter that converts the resource code, combines through runtime libraries, and also executes the resulting machine instructions all throughout runtime. Uneven a compiled language, there is no precompiled routine to run. The conversion procedure and mix with runtime libraries takes location every time an interpreted language regimen is run. This is why programs created in compiled languages have tendency to run much faster than equivalent programs created in understood languages. Click Start to run the simulation that an interpreted program. Click Restart if you want to run the simulation again.


Start Restart
each time an taken program is run, the interpreter must convert source code into an equipment code and additionally pull in the runtime libraries. This conversion procedure makes the regime run slower than a equivalent program written in a compiled language.

since an interpreter performs the counter from source to an equipment language during the running of the program, construed languages usually an outcome in programs the execute more slowly 보다 compiled programs. However what is often gained in return is that taken languages are regularly platform independent due to the fact that a various interpreter can be provided for each various operating system.

And now for something various ... Java

The Java programming language does no fit right into either the compiled language or interpreted language models. This is illustrated in the number below.


The Java compiler (javac) converts the source code into bytecode. Bytecode is a kind of average maker language. This bytecode document (.class file) can be run on any type of operating device by making use of the Java interpreter (java) for the platform. The interpreter is referred to as a virtual Machine. Thus, Java is an instance of a Virtual device programming language.

Virtual maker languages were developed to it is in a compromise in between compiled and interpreted languages. Under best conditions, virtual maker language programs operation closer in rate to compiled language programs but have the communication indepency of construed language programs.

Virtual maker languages makes use the both a compiler and an interpreter. The compiler converts the resource code into a kind of average maker language. In Java, this average an equipment language is referred to as bytecode. In visual Studio.NET languages, this average machine language is called MSIL (Microsoft intermediate Language). (To keep the discussion on this web page simpler, this compiled code will be described generically as bytecode indigenous this point on.) The interpreter for virtual an equipment languages is a special program that gives the runtime libraries because that the given operating system. That way that over there is a various virtual device interpreter for all of the supported operating systems.

The method that virtual maker programming languages obtain some that the rate of compiled languages is the the source code is run through the compiler to create the bytecode. The conversion takes place before the program is ever before run. The means that virtual device languages obtain their portability (platform independence) is by having actually a different interpreter because that each supported operating system. This interpreter ties in the correct runtime libraries for each various operating system. The compiled bytecode is an average device language that will job-related without transforms with any of the virtual machine interpreters for that language. This procedure is depicted next. We have a compiler that converts the resource code right into bytecode. This can be simulated by clicking the Compile button. When the bytecode has actually been created, that exact same bytecode can be offered without any type of changes on any type of operating system that has actually a virtual machine interpreter for the programming language. Keep in mind that every of the virtual an equipment interpreters have different runtime library code, because each operating device has different runtime libraries. This is how the virtual maker language gets approximately platform exposed problems. Click Run Windows, Run Mac OSX or Run Linux to simulate to run the routine on any kind of of those operating systems.

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translate into Run windows Run Mac OSX operation Linux
once again, note that the bytecode does not must be recompiled to run on any kind of of the various operating systems. The just reason come recompile a program is if you readjusted the source code.

Hopefully, you can see exactly how virtual machine language programs will certainly have far better performance than taken language programs. The virtual an equipment languages convert the resource code to an average device code before the regimen is ever run. Virtual machine languages don"t quite complement the power of compiled languages since the bytecode still has to be invited by the virtual device before running.

Details that the Java programming process

The resource code because that a Java regimen is a text document that end in ".java". Mean you typed the end the following file, "".

class Hello public revolution void main(String<> args) System.out.println("Hello"); come compile this program, girlfriend would type the adhering to at the command line:


The Java compiler is named javac. The javac regime is unique in that it go not develop actual device code. Rather it produce something dubbed bytecode. Unlike maker code, bytecode is no platform specific. The bytecode developed on a Windows machine is the exact same bytecode the is produced on a Linux machine. This way that the bytecode have the right to be operation (without recompiling) on any type of platform that has actually a Java interpreter.

If the compilation into bytecode is successful, the bytecode will certainly be had in a document called "Hello.class" is created. To run this bytecode, the Java interpreter is invoked in the complying with way.

java Hello

note the surname of the Java interpreter is java. Likewise note that you do not incorporate the .class at the end of the filename once invoking the interpreter. Through default, the .class record is developed in the same catalog as the magazine you room running the compiler from.

Programming tip

at this point, among the ideal ways come make progression in Java programming is to take a program that works and purposely present errors in the resource code. This will aid you to start recognizing how the compiler reports the assorted kinds of errors. Because that example, shot the following:

remove the semicolon at the finish of a statement. Remove the appropriate curly brace in ~ the end of a block. add an extra left curly brace just before the beginning of a block. Misspell words main. The main technique marks the starting point of the program.

when the error is reported, take keep in mind of the place of the error that the compiler reports. As you will see, the line the the compiler points to as having the error may not be the actual line the error wake up on.