Compiled vs interpreted language: Basics for beginning devs

A broad introduction to programming languages#

At the most fundamental level, computers understand machine language. The long-winded set of instructions made up of binary data (ones and zeros) tells the physical components, or hardware, of the computer to perform operations and transmit information to different places, and ultimately do the task the programmer wants it to do.

So, machine language became easier to write! However, programmers still had a huge problem: the amount of binary code necessary to tell the machine to perform even a simple command was (and is) frankly overwhelming. Take this example from The Scientist and Engineer’s Guide to Digital Signal Processing, by Steven W. Smith, which shows a machine code program for adding 1,234 and 4,321:

This problem led to a valuable invention: assembly language. Assembly language is a kind of shorthand or mnemonic device (to generalize) that directly correlates to binary code. Almost every computer hardware architecture has its own unique assembly language that translates to patterns of ones and zeros and ultimately tells the computer what to do. Hence the vacuum-tube programmer’s job was replaced by the assembler, a computer program holding a set of instructions determined by hardware architects to translate assembly language to machine language.

Unfortunately for programmers of the time, writing anything but the most basic program in assembly language still proved not only difficult but time-consuming. This problem again led to the establishment of additional languages correlating directly to different aspects of the assembly language (already a mnemonic device). This is where we begin to see the very first iterations of modern programming languages. One of the most widely used examples is the C language, which reads more like human English, as you can see in this code.

#include<stdio.h>
int main() {
    printf("Hello World\n");
    return 0;
}

These human-readable languages, called high-level languages, might make more sense to a programmer than binary code. But if you tried to give a computer a program in a high-level language like the code above it would do nothing. It’s not because the computer has anything against you, but simply because it doesn’t understand. It would be like giving your friend who only speaks English a guide to bake a chocolate cake, except it’s written in Urdu.

For your friend to be able to follow the guide, its instructions would need to be converted to a language your friend understands (English). This can be done by either compiling a translation of the guide and handing it over to your friend or interpreting the instructions for him while he is baking. This is where the distinction is drawn between compiled and interpreted languages. Thankfully, most modern computers come with assemblers built-in, so they won’t need translation down to the machine language (binary code) level. But they still need to be distilled to the assembly code level.

What is a compiled language?#

Compiled languages are programming languages that must be translated to machine-readable instructions using compilers, which are programs that convert human-readable source code before any code is executed. An executable file is generated, and the compiled program is then passed to the target machine for execution.

Compiled languages are fast and efficient, as the instructions are precompiled to the native language of the target machine, which then needs no assistance while executing the instructions.

Some examples of compiled languages include:

• C, C++, and C#
• Go
• Rust
• Haskell
• Cobol

What is an interpreted language?#

Interpreted languages are programming languages for which instructions are not precompiled for the target machine in a machine-readable form. Rather, these languages are assisted by an interpreter. An interpreter is a program that translates high-level, human-readable source code into low-level, machine-readable target code line by line while the interpreted program is being executed.

Interpreting the language is less efficient because the interpreter must be present for the entire process, but these languages are also highly adaptable.

Some examples of interpreted languages include:

• Python
• JavaScript
• PHP
• MATLAB
• Perl
• Ruby

Compiled vs interpreted: A comparison#

As covered in the previous two sections, compiled and interpreted languages essentially perform the same function: to translate information from the programmer-understandable language to the machine-understandable language. That said, each has its advantages and disadvantages.

Let’s return to the baking analogy. Imagine a translator had just compiled the entire chocolate cake recipe with multiple steps, only to find out that you (the programmer) discovered a new process for making one component a day later. Unfortunately, you only speak and write Urdu, and the entire recipe and process hinge on the new component. Not only must you write the entire recipe again, but the translator (compiler) needs to perform the entire process again too.

Now picture the same scenario with an interpreted language. Because the interpreter is present the entire time your friend is baking, you can very easily tell the interpreter to ask your friend to stop for a moment. You can then rewrite the new portion of the procedure yourself, edit the affected components of the recipe, and tell the interpreter to resume the process with the newly implemented procedure. Even though the process is less efficient with the interpreter, editing the instructions (program) is much simpler.

However, imagine you had a time-tested recipe for something like apple pie. Your grandparents’ grandparents passed it down to you, and it hadn’t changed in over a century. The recipe is perfect, and to add to it would do it a disservice. In this scenario, a compiled language is king. Your friend (the computer) could confidently read and carry out the instructions (program) in the most efficient way possible until the end of time without the need for disruptive iterations.

In the real world, compiled languages are preferred for computing-intensive software that requires heavy resource usage or in a distributed system where optimal performance from the processor is a key factor. Interpreted languages are preferred for less computing-intensive applications where the CPU isn’t a bottleneck, such as user interfaces. Another use case for interpreted languages was server-side development before the introduction of containers. Because the processor spent most of its time waiting for requests or replies from the database, sub-optimal performance from the processor wasn’t a concern.