The language understood by humans is very much different from one understood by machines. But then how does the input given by us be understood by the computer?
Here is when the concept of interpreters and compiler come in. These programs are built in such a way that the high-level language understood by humans is converted into a low-level or machine code. This simplifies the work of humans as they do not have to waste time on understanding another language that is anyway way too hard to interpret.
In this article, we will study the working and characteristics of an interpreter and compiler. In the end, we will differentiate them based on their features.
So, let us begin!
The software or a program built to convert any high-level language line-by-line into machine code or the language understood by the computer is called the interpreter.
Interpreters act as a medium between other programs and the computer, it helps them to run on the computer or any other server. However, during the run time the code is checked line by line. And the process does not proceed if any error is found, till corrected.
This is a very effective method of finding errors, as errors can be matched to their respective lines, however, it is a very lengthy and tiresome method. But, on the same hand, the interpreter helps the programmer to rectify its mistakes before moving onto the next step.
The interpreter converts the HLL(high-level language) or the source code into some intermediate language before finally converting it into the machine code. They are usually built for microcomputers.
On the computer, the interpreter runs the programs defined by the HLL. but despite this, source code is required to run even the interpreted source codes.
Despite being old and a slow method to process, the interpreter is helpful during large source codes. The compiler will take a large amount of time to convert a large source code but, the interpreter will do lin by line conversion and will quickly execute the lines as soon as they are getting converted.
Advantage and Disadvantage of Interpreter
The advantage is that they execute line by line thus helping coders to identify the errors.
The disadvantage is that they take a large amount of time to execute as compared to the compiler.
Applications of Interpreter
- Used for executing command languages.
- It is helpful for self-modifying codes.
- It is used in emulators as they help in running computer software that have unavailable hardware but built on modern equipment.
The working of the compiler is the same as the interpreter, however, just the working is a bit different. The interpreter focuses on each line of the source code, the compiler translates the complete code into the machine language. This is also the reason, compilers are faster than interpreters.
There are various kinds of compilers that produce outputs according to the needs. Let us look at some of them.
- Cross compiler is named so as it is a compiler that runs on a computer with a different OS or a different CPU from the one that the code is being run on.
- There is a bootstrap compiler that is written in the language which is same as the one it promises to compile.
- The decompiler, as the name suggests is the oppposite of a compiler. It converts any low level language to HLL(higher level language).
- Source-to-source compiler acts as a medium between two high level languages by translating between them. It is also known as a transcompiler.
- There are compilers that create parsers in order to perform syntax analysis. Such compilers are known as compiler-compiler.
Working and Structure of Compiler
The compiler may have many parts, but they can be classified under three primary parts- front end, middle end, and back end.
- The purpose of the front end is to verify syntaxes and semantics against a specific source language. If an error is found, it reflects error messages or warnings along side the error’s location in the source code.
The whole working of this part of the compiler includes- lexical analysis, syntax analysis, and semantic analysis. The other purpose of it is to create the input in an intermediate form also called an intermediate representation so as to become input for the middle end. So here the language is not completely converted into machine code, however, still is a lower-level language as compared to the input.
- The middle end works on the IR and does operations like – removing useless codes, reachability analysis, and constant propagation(propagation and discovery of contant values). So the whole work is to optimize the IR which are also independent of the current CPU architecture.
- The optimized IR output of the middle end is the input of the back end. The back end performs further analysis and optimizations on the IR. these all operations are target CPU specific.
Different operations of the back end include- register allocation, instructions scheduling, etc. It also performs optimizations. The main purpose is to create an ouput which is completely coverted into machine code. This machine code is made for a specific CPU and operating system.
Advantages and disadvantages of Compiler
The execution time of the compiler is much less than the interpreter. IT also completely analyzes the source code before moving forward. This is the biggest advantage of the compiler. However, as it translates the whole code at one go, to rectify each mistake one has to go back to the source code. This is one disadvantage of it.
Difference between compiler and interpreter
Hopefully, by now you must have understood the working and different characteristics of the compiler and interpreter both. Here are a few of the many differences between both programs. Let us look at them one by one.
|The compiler scans the whole code and converts it in one go.||The interpreter interprets or converts one line of source code at a time.|
|All the errors in the source code file are reflected in the end, as it is compiled in one go.||The errors are shown line by line as the interpreter goes through the code.|
|The compiler converts in 3 steps so it needs more memory to store the codes in the intermediary step as well,||The interpreter translates directly into the machine code therefore there is no need for extra memory.|
|Debugging is relatively harder as the code is compiled at once||Debugging is relatively easier.|
|The source code is not required once the translation is over.||The source code is required each time the program is run, after the translation.|
|The compiler takes a good time to analyze and optimize the source code.||The interpreter does not put too much effort into analyzing the source code.|
|The execution time of the compiler is much lesser.||The execution time of the interpreter is higher.|
|It stores the machine code translated from the source code onto the disk.||It does not store the machine code onto the disk|
|The machine code is stored in a separate .exe file.||It does not store the machine code anywhere separately, and this is why it requires source code to execute the program.|
|Compilers are best suited for languages like C, C++, C#, etc.||Interpreters are best suited for languages like RUBY, MATLAB, Python, etc.|
Each of these software has its own advantages and disadvantages, therefore, it is quite tough to decide which precedents which one. So depending on the OS, CPU, and the language being used, compiler and interpreter are chosen.
Kuldeep is the founder and lead author of ArtOfTesting. He is skilled in test automation, performance testing, big data, and CI-CD. He brings his decade of experience to his current role where he is dedicated to educating the QA professionals. You can connect with him on LinkedIn.