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Dart Comments

A comment is a note written in code for people to read. Dart ignores every comment when a program runs.

A comment above code

The note above the print explains that line. Only the greeting reaches the screen.

void main() {
  // Show a greeting
  print('Hello');
}

A comment after code

The note after the code explains that print line. The shown word is the only output.

void main() {
  print('Hello again'); // Show another greeting
}

A block comment

The block note spans two lines above the print lines. Both shown words still appear in order.

void main() {
  /* Show two short lines
     Each line shows one word */
  print('First');
  print('Second');
}

Example

void main() {
  // Show the title
  print('Morning');
  /* Show the next line
     The step shows below this note */
  print('Tea');
}

Key points

  • Use // to start a line comment.
  • A line comment runs to the end of its line.
  • Use /* to open a block comment and */ to close it.
  • A comment can sit above a line of code or after code on the same line.

In this example, a line comment sits above the first print, and that print shows Morning. A block comment sits above the second print, and that print shows Tea. No comment text reaches the screen.

Note

A program with comments gives the same output as the same program without them.

Try it Yourself

Edit the code, then press Run.

Running is simulated · DartPad

Exercise

What does Dart do with a comment?