An interpreter translates programming language statements in a different way than a compiler. Rather than creating a compile object module for a program, an interpreter reads, translates and executes the source program one line at a time. IT performs the translation into machine language while the program runs. Interpreters offer both advantages and disadvantages compared with compilers. Two major advantages are that interpreters are easier to use, and because the execution usually stops at the point where an error is encountered. They help programmers to discover errors in programs easily. The interpreter program itself requires relatively little storage space, and it does not generate an object module to occupy still more storage space. For these reasons, interpreters provide ideal tools for beginning programmers and non programmers. The major disadvantage of interpreters is that they work less efficiently than compilers do, so interpreted programs run more slowly than compiled programs. Because an interpreter translates each program statement into machine language just before executing it, it can chew up a lot of time especially when the program must repeatedly execute the same statements thousands of times, reinterpreting each one every time. In contrast, a compiler translates each program statement only once before program execution begins. In addition by sorting the object module of a compiled program on disk, the programmer can avoid the need to retranslate the source program every time the program runs.
An interpreter is a computer program that essentially compiles and executes (interprets) another computer program "on-the-fly" at runtime.
In computer science the term "interpreter" is sometimes used instead of the term emulator. There are software interpreters and hardware interpreters. We will denote interpreter as a software interpreter. It can also refer to a program that performs compilation as well as emulation. Most interpreters available today generally compile source code when the code is first encountered during program execution, rather than in a separate phase prior to execution.
An interpreter has a number of advantages over a compiler, including:
Because it can be tailored to a specific programming language making it simpler to implement and more compact (BASIC was supported on many early home computers for this reason). it allows program implementation to be independent of the characteristics of the host cpu (the Java interpreter is a good example of this). The main disadvantage of interpreters is that when a program is interpreted, it runs slower than if it had been compiled. The difference in speeds could be tiny or great; often an order of magnitude and sometimes more.
You must understand interpreter in different conditions and on different positions. In simple words interpreter is the person who orally translates from one language to another language. For example, if a head of state is speaking in United Nation's meeting then it is very obvious that many people would not understand his language. To translate his address so that all people can understand the interpreter are designated to do this job. They translate the language of the speaker in the desired language. There is another type of the interpreter I'm giving information about them below.
When a computer program is designed in some computer language like Java, C or C++ then computer needs to understand the instructions which are given in that language. So these instructions are translated by a program into a machine language that is also called the interpreter.
So there are basically 2 types of interpreter which I've mentioned. One is the real human beings who translate the language of the words in the other desired languages while on the other side the interpreter of computer works to convert some computer language in machine language. I hope this answer is sufficient for you to understand.
An interpreter is programme that translates a high-level programming language into machine language during the actual step-by-step execution of a programme. Translation and execution alternate for each statement encountered in the high-level language programme. In other words, an interpreter translate one instruction, and the control unit execute the resulting, machine language, the next instruction is translated, and the control unit execute the machine language instruction, and so on. If the programme is sun seven times a day, the programming language is reinterpreted seven times. In case of a compiler, the whole source program is translated into an equivalent machine language programme. The object programme, thus obtained is permanently saved for future used and is used every time the programme is to be executed. So repeated compilation is not necessary for repeated execution of a programme. However, in case of an interpreter, no object programme is saved for future use because the translation and the execution processes alternate. The next time an instruction is used, it must once again be interpreted and translated into machine language. For example, during the repetitive processing of the instruction with in a loop, each instruction in a loop will have to be reinterpreted every time the loop is executed.
