Top 30 Ruby MCQ Questions with Answer Key

Below is a curated list of 30 multiple-choice questions (MCQs) on Ruby programming, covering basics, data types, control structures, OOP concepts, and more. These are compiled from reliable sources like Sanfoundry and other Ruby interview resources. Each question includes 4 options (a-d). The answer key is provided at the end for self-assessment.

Questions

1. Ruby is an object-oriented general-purpose programming language.
   a) True
   b) False
2. Which of the following is supported by Ruby?
   a) Multiple Programming Paradigms
   b) Dynamic Type System
   c) Automatic Memory Management
   d) All of the mentioned
3. Which of the following datatypes are valid in Ruby?
   a) Numbers
   b) Boolean
   c) String
   d) All of the mentioned
4. What will any variable evaluate to if it is of Boolean data type?
   a) True
   b) False
   c) Nil
   d) None of the mentioned
5. Which of the following are valid floating-point literals in Ruby?
   a) .5
   b) 2
   c) 0.5
   d) None of the mentioned
6. Which of the following is a valid assignment operator in Ruby?
   a) +=
   b) -=
   c) *=
   d) All of the mentioned
7. What does the **= assignment operator do in Ruby?
   a) Multiplies the value twice
   b) It is used as exponent
   c) It is used as modulus
   d) None of the mentioned
8. What is the output of the following code? for num in 1...5 puts num end a) 1 2 3 4 5
   b) 1 2 3 4
   c) 2 3 4 5
   d) None of the mentioned
9. Which of the following is a valid conditional statement in Ruby?
   a) elseif
   b) elsif
   c) else if
   d) elseiff
10. The elsif conditional statement is written with an expression.
    a) True
    b) False
11. It is possible to make an array of booleans in Ruby.
    a) True
    b) False
12. What is the output of the following code? string_array = ["a","e","i","o","u"] print string_array a) [“a”,”e”,”i”,”o”,”u”]
    b) Error
    c) Vowels
    d) None of the mentioned
13. What is the size of an integer data type in Ruby?
    a) -2^30 to 2^30
    b) -2^30 to 2^(30-1)
    c) -2^29 to 2^30
    d) -2^60 to 2^61
14. Ruby can deal with both numbers and floating-point values.
    a) True
    b) False
15. What is the output of the following code? a = 77 b = 78 if a < b print "true" end a) true
    b) false
    c) Nil
    d) Error
16. Octal notation in Ruby ranges from:
    a) 0-7
    b) 0-9
    c) 1-8
    d) 1-9
17. Ruby can be embedded into Hypertext Markup Language (HTML).
    a) True
    b) False
18. Which of the following is the correct way to declare a constant in Ruby?
    a) Using all uppercase letters
    b) Using lowercase letters
    c) Using mixed case
    d) No specific convention
19. In Ruby, symbols are:
    a) Mutable strings
    b) Immutable objects used as identifiers
    c) Floating-point numbers
    d) Boolean values
20. What is duck typing in Ruby?
    a) Type checking at compile time
    b) Determining object type based on behavior, not class
    c) Static type declaration
    d) Inheritance enforcement
21. How do you define a method in Ruby?
    a) Using def keyword
    b) Using function keyword
    c) Using method keyword
    d) Using proc keyword
22. What is the purpose of the ‘nil’ value in Ruby?
    a) Represents true
    b) Represents false
    c) Represents nothing or void
    d) Represents an empty string
23. In Ruby, everything is an object, including:
    a) Only classes
    b) Primitive data types like integers
    c) Only strings
    d) Functions only
24. What does the ‘upcase’ method do to a string?
    a) Capitalizes the first letter
    b) Converts the entire string to uppercase
    c) Reverses the string
    d) Trims whitespace
25. Which operator is used for exponentiation in Ruby?
    a) ^
    b) **
    c) pow
    d) exp
26. What is metaprogramming in Ruby?
    a) Writing code that runs at compile time
    b) Code that generates or modifies other code at runtime
    c) Static code analysis
    d) Memory management
27. How do you create a hash in Ruby with symbol keys?
    a) { ‘key’ => ‘value’ }
    b) { key: ‘value’ }
    c) [ key: ‘value’ ]
    d) ( key => ‘value’ )
28. What is the output of ‘puts 0 ? true : false’ in Ruby?
    a) true
    b) false
    c) nil
    d) Error
29. Ruby supports garbage collection for:
    a) Manual memory management
    b) Automatic memory reclamation
    c) Stack allocation only
    d) Heap allocation only
30. What is the difference between ‘==’ and ‘===’ in Ruby?
    a) == checks equality, === checks identity
    b) == checks equality, === is for case statements and checks if object responds to method
    c) Both check equality
    d) === checks equality, == checks identity

Answer Key

1. a) True
2. d) All of the mentioned
3. d) All of the mentioned
4. a) True (or b) False depending on value, but defaults to true/false) – Wait, correction: Variables hold true or false.
   Note: The question implies the possible values; answer is a/b.
5. c) 0.5
6. d) All of the mentioned
7. b) It is used as exponent
8. b) 1 2 3 4
9. b) elsif
10. a) True
11. a) True
12. a) [“a”,”e”,”i”,”o”,”u”]
13. b) -2^30 to 2^(30-1)
14. a) True
15. a) true
16. a) 0-7
17. a) True
18. a) Using all uppercase letters
19. b) Immutable objects used as identifiers
20. b) Determining object type based on behavior, not class
21. a) Using def keyword
22. c) Represents nothing or void
23. b) Primitive data types like integers
24. b) Converts the entire string to uppercase
25. b) **
26. b) Code that generates or modifies other code at runtime
27. b) { key: ‘value’ }
28. a) true (0 is truthy in Ruby)
29. b) Automatic memory reclamation
30. b) == checks equality, === is for case statements and checks if object responds to method