Comments and documentation markup in Swift - Step-by-Step Execution

Concept Flow - Comments and documentation markup

Start Code

↓

Read Line

↓

Is it a Comment?

No→Execute Code

Yes↓

Ignore or Use for Docs

↓

Next Line

↩Back to Read Line

The program reads each line, checks if it's a comment or documentation markup, then either ignores it or uses it for docs, otherwise executes the code.

Execution Sample

Swift

/// Adds two numbers
func add(a: Int, b: Int) -> Int {
    // Return sum
    return a + b
}

This Swift code shows a documentation comment for a function and a normal comment inside the function.

Execution Table

Step	Line Read	Is Comment?	Comment Type	Action	Output
1	/// Adds two numbers	Yes	Documentation	Store for docs
2	func add(a: Int, b: Int) -> Int {	No	Code	Execute function declaration
3	// Return sum	Yes	Single-line comment	Ignore during execution
4	return a + b	No	Code	Return sum of a and b
5	}	No	Code	Close function

💡 End of code reached, all comments processed or ignored, function declared.

Variable Tracker

Variable	Start	After Step 2	After Step 4	Final
Function add	undefined	Declared	Ready to call	Declared

Key Moments - 2 Insights

Why does the documentation comment start with /// instead of //?

/// marks a documentation comment that tools use to generate docs, while // is a normal comment ignored by tools. See step 1 in execution_table.

Does the single-line comment inside the function affect the program output?

No, single-line comments like // Return sum are ignored during execution, as shown in step 3.

Visual Quiz - 3 Questions

Look at the execution table, what action is taken at step 1?

A Execute the code line

B Ignore the comment completely

C Store the documentation comment for docs

D Return a value

💡 Hint

Check the 'Action' column at step 1 in the execution_table.

At which step is the function declared?

A Step 1

B Step 2

C Step 3

D Step 4

💡 Hint

Look for 'Execute function declaration' in the Action column.

If the comment on step 3 was removed, what would change in the execution?

A Nothing changes in execution

B The output would change

C The function would not work

D The documentation would be missing

💡 Hint

Step 3 comment is ignored during execution, so removing it does not affect output.

Concept Snapshot

Swift comments:
// single-line comment ignored by compiler
/// documentation comment used by tools
/* multi-line comment */ for longer notes
Comments do not affect code execution but help explain code.

Full Transcript

This example shows how Swift reads code lines and identifies comments. Documentation comments start with /// and are stored for generating docs. Single-line comments with // are ignored during execution. The function is declared normally. Comments help explain code but do not change how it runs.