Source: https://senecalearning.com/en-gb/revision-notes/gcse/coding/national-curriculum/4-2-1-comments

[Revision notes](https://senecalearning.com/en-gb/revision-notes.md) › [GCSE](https://senecalearning.com/en-gb/revision-notes/gcse.md) › [Coding](https://senecalearning.com/en-gb/revision-notes/gcse/coding.md) › [National Curriculum](https://senecalearning.com/en-gb/revision-notes/gcse/coding/national-curriculum.md) › Comments

# Comments

Coding: Introduction to Python v3, topic 4.2.1

## Comments

Comments are lines of code that are ignored completely by the computer.

### What are comments?

![What are comments?](https://image-v2.cdn.app.senecalearning.com/2018-08/162779ec-f6d5-4383-b04b-99e5825aa2d2/comments-click-mouse-.jpg)

- A comment is a line of code that is completely ignored by the computer.
- Comments can be used to add description to your code to make it easier for other people to understand.
- They can also be used to leave notes and reminders to yourself as you work on a complex program.

### How to comment

![How to comment](https://image-v2.cdn.app.senecalearning.com/2018-08/29575f00-f258-4c98-945f-f5986f526be5/Number-hashtag-.png)

- To write a comment in most languages, you must use a special character which tells the computer to ignore the rest of the line:
 - In Python, that character is a #.

### Interfaces

![Interfaces](https://image-v2.cdn.app.senecalearning.com/2018-09/3fba2487-0107-4ee7-9e33-50edfe5b6f04/checklist-ticklist-tick-list-.jpg)

- An interface is a collection of comments which describe a subroutine.
- An interface includes:
 - List of parameters and their types.
 - Return value and its type.
 - What the subroutine does.

### Interface example

![Interface example](https://image-v2.cdn.app.senecalearning.com/2018-08/b4963498-d283-4c39-8783-06d2dc42f330/Interfaces.png)

## Test yourself on Comments

- How do you start a single-line comment in Python?

[Practise this topic for free](https://app.senecalearning.com/classroom/course/72d0364c-db0a-4630-8e0a-61f48cae0252/section/19a88f45-319e-41da-930e-c119bf10dda6/session)

- Previous topic: [4.1.2 Whitespace](https://senecalearning.com/en-gb/revision-notes/gcse/coding/national-curriculum/4-1-2-whitespace.md)
- Next topic: [4.3.1 Exceptions](https://senecalearning.com/en-gb/revision-notes/gcse/coding/national-curriculum/4-3-1-exceptions.md)

## Coding: Introduction to Python v3 contents

### 1 Introduction to Python
- 1.1 Python
  - [1.1.1 Python](https://senecalearning.com/en-gb/revision-notes/gcse/coding/national-curriculum/1-1-1-python.md)
- 1.2 Input & Output
  - [1.2.1 Input & Output](https://senecalearning.com/en-gb/revision-notes/gcse/coding/national-curriculum/1-2-1-input-and-output.md)
- 1.3 Data Types
  - [1.3.1 Data Types](https://senecalearning.com/en-gb/revision-notes/gcse/coding/national-curriculum/1-3-1-data-types.md)
- 1.4 Variables & Constants
  - [1.4.1 Variables & Constants](https://senecalearning.com/en-gb/revision-notes/gcse/coding/national-curriculum/1-4-1-variables-and-constants.md)
- 1.5 Operators
  - [1.5.1 Arithmetic & Relational Operators](https://senecalearning.com/en-gb/revision-notes/gcse/coding/national-curriculum/1-5-1-arithmetic-and-relational-operators.md)
  - [1.5.2 Boolean & Assignment Operators 2](https://senecalearning.com/en-gb/revision-notes/gcse/coding/national-curriculum/1-5-2-boolean-and-assignment-operators-2.md)
- 1.6 Program Flow
  - [1.6.1 Selection](https://senecalearning.com/en-gb/revision-notes/gcse/coding/national-curriculum/1-6-1-selection.md)
  - [1.6.2 Iteration](https://senecalearning.com/en-gb/revision-notes/gcse/coding/national-curriculum/1-6-2-iteration.md)

### 2 Data Structures
- 2.1 Lists & Strings
  - [2.1.1 Lists](https://senecalearning.com/en-gb/revision-notes/gcse/coding/national-curriculum/2-1-1-lists.md)
  - [2.1.2 Strings](https://senecalearning.com/en-gb/revision-notes/gcse/coding/national-curriculum/2-1-2-strings.md)
- 2.2 File Handling
  - [2.2.1 File Handling](https://senecalearning.com/en-gb/revision-notes/gcse/coding/national-curriculum/2-2-1-file-handling.md)

### 3 Modularity
- 3.1 Subroutines
  - [3.1.1 Subroutines](https://senecalearning.com/en-gb/revision-notes/gcse/coding/national-curriculum/3-1-1-subroutines.md)
- 3.2 Data Flow
  - [3.2.1 Data Flow](https://senecalearning.com/en-gb/revision-notes/gcse/coding/national-curriculum/3-2-1-data-flow.md)

### 4 Good Practice
- 4.1 Naming & Whitespace
  - [4.1.1 Identifiers](https://senecalearning.com/en-gb/revision-notes/gcse/coding/national-curriculum/4-1-1-identifiers.md)
  - [4.1.2 Whitespace](https://senecalearning.com/en-gb/revision-notes/gcse/coding/national-curriculum/4-1-2-whitespace.md)
- 4.2 Comments
  - [4.2.1 Comments](https://senecalearning.com/en-gb/revision-notes/gcse/coding/national-curriculum/4-2-1-comments.md)
- 4.3 Exceptions
  - [4.3.1 Exceptions](https://senecalearning.com/en-gb/revision-notes/gcse/coding/national-curriculum/4-3-1-exceptions.md)