Source code is the underlying set of instructions that makes any website, app, or computer program work. Source code is used in everything from simple websites to spacecraft and it comes in many varieties. There are different programming languages one can use to write source code and different ways source code is used to create working software, such as compiled or interpreted code.
Structure of source code
Source code can vary wildly, depending on the programming language used, but in essence, a file (often many) is used to contain code in a plain text format. While programming languages are not quite like natural languages, they have something in common: the exact rules of grammar and vocabulary will differ by language, but all will have some form of grammar and structure to them. In the same way, most programming languages will support the features below in some way.
Variables are used to contain information that varies, hence the name. Virtually every programming language supports variables and any software that accepts user input is highly likely to use them. A good use of an example of variables is an e-commerce checkout page. The structure and layout of the page will be the same for all users, but variables are used to contain the products in the basket, address information, and order instructions, that may differ from order to order.
Variables can contain different types of information. For example, a whole number such as "5" is called an integer, a word like "dog" is a string, and a simple true/false variable is called a boolean.
let apples = 5;
The variable 'apples' now contains the value 5 and may be referred to in code. Other common statements in programming languages include switches, while loops, if/else statements, and more.
Comparison operators are characters used to make comparisons, typically between two different variables. Comparison operators work differently, both depending on the programming language and the type of comparison wanted.
Comments are not generally executed by a program, but instead, they are useful for the programmers that write the code. The software can easily become very complicated, with a large program being split into many different files, and each file may contain hundreds of lines of code.
// A comment is a piece of text that will not be run or interpreted by the program.
Creating source code
Source code can be written in many ways. Many developers choose to use an IDE (Integrated Developer Environment) to help write source code. An IDE will typically include many features that are extremely useful for developers, such as auto-complete, code hints, debugging, code highlighting, and more.
Source code of a website
Websites in particular will use a language such as PHP to create the flow and content of a website. For example, a blog article will use something like PHP to extract information like the title, author, date, and blog content from a database to be displayed on a page. HTML is then used to create the layout for a blog to display that information, and CSS is used to add stylistic information, like which fonts to use, the font sizes, colors, and other design elements. All current web browsers offer their users the possibility to view the code of a website. This is usually done by pressing CTRL+U.
Screenshot with example source code of seobility.net
Importance for SEO
Source code is very important for SEO, as it is the foundation of websites and apps. Everything from the way in which a website works, to how fast pages load, is determined at least partially by the source code. Poorly-written or poorly optimized code may load slower, which will affect page speed and, in turn, site ranking on search engines.
Source code also dictates which features a website may support, which can in turn affect SEO. Fundamentals like including meta tags, properly labeling website sections, adding alternative text to images, optimizing layouts for different screen sizes, and more contribute towards SEO and are all controlled by the underlying programming.