Source code: What exactly is it?

Computers - regardless of whether it’s a home PC, modern smartphone, or scientific computer - work in the binary system: on/off, loaded/not loaded, 1/0. A sequence of bits instructs the computer as to what it should do. While commands were created in this way in the early days of computer technology, we have long since switched to writing applications in a human-readable programming language. This may sound strange at first since source code could also look like confused gibberish to a layman.

In context, “human-readable” is understood as the counterpart to the term “machine-readable”. While computers only work with number values, humans communicate with words. So, just like a foreign language, one must learn at least one of the various programming languages before being able to program, etc.

Different programming languages

There are hundreds of different programming languages. It’s impossible to say for certain which are better or worse, as it depends on the context of the project and the application for which the source code is used. Some of the most popular programming languages are:

• BASIC
• Java
• C
• C++
• Pascal
• Python
• PHP
• JavaScript

For the computer to understand these languages, however, they need to first be translated into machine code.

Compiler & Interpreter

For the computer to be able to further process the source code written by the programmer, there needs to be a translation between the two – this occurs in the form of an additional program. This assistance application can be in either the form of a compiler or an interpreter:

• Compiler: This application type translates (compiles) the source code into a code that the process understands and can execute. This machine code is saved in the form of an executable file.
  
  
• Interpreter: An interpreter translates the source code line for line and executes it directly. The translation process is much faster than a compiler but the execution is slower and requires a large amount of memory.

You don’t get to choose, either: each programming language determines whether a compiler or an interpreter is used in combination with it. Nowadays, an intermediate solution is being used increasingly often - Just-in-time compilation (JIT). This type of translation attempts to combine the advantages of both variants (quick analysis and quick execution) and is used in browsers, for example, to more effectively handle JavaScript, PHP, or Java.

Markup languages

The foundation of a website is also referred to as a source code. However, this is not a case of a programming language but rather the markup language HTML. A markup language determines how content is structured. For example, using HTML allows you to define headlines, paragraphs, or highlights. An HTML document isn’t a program in and of itself but may contain one, for example in the form of JavaScript Code. A similar principle applies for other markup languages, such as XML.

Depending on the programming language in question, you’re limited to certain conventions when writing a program. Very few programming languages appear out of nowhere, though, and most of them build on one another. For this reason, certain elements come into use in various different program codes:

• Commands: Instructions are as a rule the basis for all applications. Here, the programmer makes it clear for their future program what needs to be done. Such commands can, for example, trigger certain calculations or display a text.
  
  
• Variables: Variables are vacancies that can be filled with information. These are referred to within the source code again and again with an assigned name.
  
  
• Comparisons: The structure of most programs is built by queries that function on the if-then scheme, i.e. the principle of propositional logic. If a particular truth value is entered, then one solution is triggered instead of another.
  
  
• Loop: Queries can also be the foundation for loops in a source code. A command is repeated until a certain value is reached. When the program ends the loop and runs the rest of the code.
  
  
• Comments: In all common programming languages, you can comment on lines within the code. This makes it possible to write text in the source code that isn’t taken into account by the program. Comments are entered into the source code, for example, so that you or another developer can continue to understand parts of the code in the future.

With the creation of a source code, there’s always a problem to solve. Developers write programs in order to provide solutions. The way to do that, though, is not set in stone. When two programmers are dealing with the same problem, it could well happen that the two resulting source codes are quite different from one another - even if they are working in the same language.

Even though in many cases there isn’t one right answer, all programming work has one thing in common - a good source code avoids unnecessary text. The additional text makes the problem confusing, slower, and more prone to errors. Particularly confusing source code that even professionals can’t read is referred to as spaghetti code since the structure may be as tangled as dangly pasta on a plate.

To write a source code, all you really need is a simple text editor - like the Notepad on Windows or TextEdit on Mac. This way, source code can be saved as plain text (e.g. in ASCII coding  or with UTF-8 encoding) with the correct file name ending for the programming language. So if you find a file with the ending “.cpp” on your hard drive, then it’s actually a text file, likely containing code in the C++ programming language.

Integrated development environment (IDE)

Enormous projects can be realized more easily with special programs. Integrated development environments combine multiple tools that developers need for their work (hence, “integrated”), speeding up the workflow. Other advantages of such IDEs are the tools that communicate with one another seamlessly and make synchronous changes. These tools usually include:

• Text editors: The text editor is also a core piece of the development environment. Although a few visual programming languages exist that function through the arrangement of graphical elements, the vast majority of applications are written using classic source code. Text editors that are part of an IDE have a similar range of functions as editors that are used for programming outside of an environment.
   
• Compiler/Interpreter: IDEs also contain a compiler and/or interpreter. This way, programmers can run their code directly from the environment.
   
• Debugger: The use of a debugger is essential for sensible programming work. This tool is also a standard component of an integrated development environment. With this tool, you can search your source code for errors (bugs) by using breakpoints to interrupt the flow of the program and analyze the executed processes.
   
• Linker: To finish off a compilation process, various elements have to be merged. A linker is a program that carries out this task and creates an executable file.
   
• Version management: This tool records all of the changes that you make to the source code and can restore older versions of the code. This way, your entire project is not in danger if you accidentally make an error. A version management tool is also essential when multiple developers are working together on the same project.
   
• GUI builder: Part of many applications is a graphical user interface (GUI). Of course, this also has to be defined in the source code. A GUI builder supports developers when designing the interface. In the form of a WYSIWYG editor, you can often organize graphic elements using drag-and-drop. The GUI builder translates these into functions of the programming language within the IDE.

Well-known examples of the integrated development environment are the open source Eclipse or the Microsoft product Visual Studio.