What is declarative programming, and what are examples like HTML and SQL?

Declarative programming is a paradigm where the desired result is described, rather than the sequence of steps to achieve it. The programmer tells the system what needs to be done, not how.

Examples:

• HTML (HyperText Markup Language): A markup language that describes the structure and content of a web page. You define elements (headings, paragraphs, links), and the browser interprets this markup for display.

  <!-- Level one heading -->
  <h1>Hello World!</h1> 
  
  <!-- Regular paragraph -->
  <p>This is an example of a declarative approach in HTML.</p> 
  

• SQL (Structured Query Language): A language for managing relational databases. You describe what data you want to retrieve or modify, and the database management system (DBMS) determines the optimal way to execute the query.

  -- Select all records from the users table
  -- where age is greater than 18
  SELECT * 
  FROM users 
  WHERE age > 18;
  

Key differences from imperative programming (which describes step-by-step algorithms):

Criterion	Declarative Programming	Imperative Programming
Focus	What to do	How to do
Description	Desired result	Sequence of operations
Flexibility	DBMS/interpreter determines the method	Programmer determines the method
Examples	SQL, HTML, CSS, Prolog	Java, C++, Python (to a large extent), JavaScript