Comments and documentation in Ruby - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of code with inline and block comments

What is the output of this Ruby code that uses both inline and block comments?

Ruby

puts 5 + 3 # adds five and three
=begin
This is a block comment
It should be ignored by Ruby
=end
puts 2 * 4

A 8\n2 * 4

B SyntaxError

C 5 + 3\n2 * 4

D 8\n8

💡 Hint

Remember that comments do not affect the output and are ignored by Ruby.

The inline comment after 'puts 5 + 3' is ignored, so 8 is printed. The block comment between =begin and =end is also ignored. Then 'puts 2 * 4' prints 8.

❓ Predict Output

intermediate

Effect of comments on variable assignment

What will be the value of variable x after running this Ruby code?

Ruby

x = 10 # initial value
# x = 20
x = 30 # updated value

A 30

B nil

C 20

D 10

💡 Hint

Lines starting with # are ignored by Ruby.

The line 'x = 20' is commented out, so it does not run. The last assignment 'x = 30' sets x to 30.

🔧 Debug

advanced

Identify the syntax error caused by incorrect comment usage

Which option shows code that will cause a syntax error due to incorrect comment usage in Ruby?

A # This is a valid comment\nputs 'World'

B =begin\nThis is a block comment without an end

C puts 'Hello' # This is a comment

D puts 'Test' # Another comment

💡 Hint

Block comments must have both =begin and =end.

Option B starts a block comment with =begin but does not close it with =end, causing a syntax error.

🧠 Conceptual

advanced

Purpose of documentation comments in Ruby

What is the main purpose of documentation comments in Ruby code?

A To add extra functionality to the program

B To make the code run faster

C To explain the code to humans without affecting execution

D To cause errors if the code is incorrect

💡 Hint

Think about why programmers write comments.

Documentation comments help humans understand the code. They do not change how the program runs.

❓ Predict Output

expert

Output of code with nested comments and string literals

What is the output of this Ruby code snippet?

Ruby

puts "Hello # not a comment"
# puts "This line is commented out"
=begin
puts "This is inside a block comment"
=end
puts 'Goodbye'

A Hello # not a comment\nGoodbye

B Hello\nGoodbye

C Hello # not a comment\nThis line is commented out\nGoodbye

D SyntaxError

💡 Hint

Comments do not affect strings inside quotes.

The string "Hello # not a comment" prints exactly as is because # inside quotes is not a comment. The commented out puts line and block comment are ignored. Then 'Goodbye' prints.