Compilers vs. interpreters: explanation and differences

When choosing a programming language, two things, in particular, need to be taken into consideration: the language needs to provide all the necessary building blocks for the planned software project, and programming and implementing the project should be as simple as possible. Being easy to read and having simple code is essential to ensuring the latter because these characteristics make it easier to get started with and learn a programming language, as well as to use it on a daily basis.

In order for the instructions of a written program to then be understood by a computer or processor, the source code of modern programming languages must first be converted into a machine-readable form. This is done with either a compiler or an interpreter depending on the programming language. What exactly do these two tools do? And how do they differ from one another?

What is an interpreter?

An interpreter is a computer program that processes the source code of a software project during its runtime (i.e. while it is running) and acts as an interface between the project and the processor. Interpreters always handle code line by line so that the individual instructions of each line are read, analyzed and converted for the processor one after another. This also applies to recurring instructions which are executed each time they occur. Interpreters use their own internal libraries to process software code: once a line of source code has been converted into the corresponding machine-readable instructions, it is sent directly to the processor.

The conversion process is not complete until all the code has been interpreted. It will only stop early if an error has occurred during the processing. This makes debugging much easier since the line of code containing the bug is immediately identified when the error occurs.

What is a compiler?

A compiler is a computer program that converts the source code of a software project in its entirety into machine code before it is run. Only then is the project run by the processor which means it has all the instructions available to it in machine code right from the start. The processor thus has all the necessary parts ready to run the given software, process input and generate output. In many cases, there is a crucial intermediate step which takes place during the compiling process: before being converted into machine code, most compilers will often first convert it into an intermediate code (i.e. ?object code) which is often compatible with various platforms and can also be used by an interpreter.

When generating the code, compilers determine the order in which instructions are sent to the processor. If the instructions are not dependent on one another, the processor can even execute the instructions simultaneously.

Compilers vs. interpreters: overview of the differences in a table

Both compilers and interpreters are used to convert written software code into a machine-readable executable format. Computer processors require this converted code in order to run programs in languages such as C, C++, PHP, Python and Ruby which makes these two tools essential for using desktop computers, laptops and smartphones. The brief descriptions given above have already shown that there are important differences between compilers and interpreters which must be taken into consideration, particularly when choosing the right programming language for new software.