Compiled and Interpreted Languages

Many languages are compiled languages. When you write assembly language, each instruction you write is translated into exactly one machine instruction for processing. With compilers, a statement can translate into one or hundreds of machine instructions. In fact, depending on how advanced your compiler is, it might even restructure parts of your code to make it faster. In assembly language what you write is what you get.

There are also languages that are interpreted languages. These languages require that the user run a program called an interpreter that in turn runs the given program. These are usually slower than compiled programs, since the interpreter has to read and interpret the code as it goes along. However, in well-made interpreters, this time can be fairly negligible. There is also a class of hybrid languages which partially compile a program before execution into byte-codes. This is done because the interpreter can read the byte-codes much faster than it can read the regular language.

There are many reasons to choose one or the other. Compiled programs are nice, because you don't have to already have an interpreter installed in the user's machine. You have to have a compiler for the language, but the users of your program don't. In an interpreted language, you have to be sure that the user has an interpreter installed for your program, and that the computer knows which interpreter to run your program with. However, interpeted languages tend to be more flexible, while compiled languages are more rigid.

Language choice is usually driven by available tools and support for programming methods rather than by whether a language is compiled or interpretted. In fact many languages have options for either one.

High-level languages, whether compiled or interpreted, are oriented around you, the programmer, instead of around the machine. This opens them up to a wide variety of features, which can include the following:

• Being able to group multiple operations into a single expression

• Being able to use "big values" - values that are much more conceptual than the 4-byte words that computers normally deal with (for example, being able to view text strings as a single value rather than as a string of bytes).

• Having access to better flow control constructs than just jumps.

• Having a compiler to check types of value assignments and other assertions.

• Having memory handled automatically.

• Being able to work in a language that resembles the problem domain rather than the computer hardware.

So why does one choose one language over another? For example, many choose Perl because it has a vast library of functions for handling just about every protocol or type of data on the planet. Python, however, has a cleaner syntax and often lends itself to more straightforward solutions. Its cross-platform GUI tools are also excellent. PHP makes writing web applications simple. Common LISP has more power and features than any other environment for those willing to learn it. Scheme is the model of simplicity and power combined together. C is easy to interface with other languages.

Each language is different, and the more languages you know the better programmer you will be. Knowing the concepts of different languages will help you in all programming, because you can match the programming language to the problem better, and you have a larger set of tools to work with. Even if certain features aren't directly supported in the language you are using, often they can be simulated. However, if you don't have a broad experience with languages, you won't know of all the possibilities you have to choose from.