What is comments?

Comments are short notes that programmers write inside their code to explain what a piece of code does, remind themselves of why they wrote it that way, or leave instructions for other developers. The computer ignores comments when it runs the program, so they don’t affect how the software works.

Let's break it down

  • Syntax: Every programming language has its own way to start a comment, like // for a single line in JavaScript, # in Python, or /* ... */ for multi‑line comments in C.
  • Placement: Comments can be placed on their own line above code, at the end of a line of code, or spanning several lines.
  • Content: Good comments describe the why (reason or intention) more than the what (the code itself), because the code already shows what it does.

Why does it matter?

Comments make code easier to read and understand, especially when a project grows or when new people join the team. They help prevent mistakes, speed up debugging, and serve as documentation that can be turned into user guides or API references.

Where is it used?

  • In every software project, from tiny scripts to massive applications.
  • In open‑source repositories where many contributors need to understand each other’s work.
  • In educational code examples and tutorials to teach concepts step by step.
  • Inside configuration files, scripts, and even markup languages like HTML (<!-- comment -->).

Good things about it

  • Clarity: Explains complex logic in plain language.
  • Collaboration: Helps teammates quickly grasp intent.
  • Maintenance: Makes future updates safer and faster.
  • Self‑documentation: Reduces the need for separate documentation files for simple explanations.

Not-so-good things

  • Outdated comments: If the code changes but the comment doesn’t, it can mislead developers.
  • Over‑commenting: Too many obvious comments clutter the code and reduce readability.
  • Inconsistent style: Different comment formats across a project can look messy and cause confusion.
  • Performance myth: Some think comments affect runtime speed, but they are stripped out during compilation or ignored by interpreters.