MCQs on Swift Fundamentals | Swift

Dive into Swift Fundamentals to strengthen your programming foundation. Learn about variables, constants, data types, type inference, type safety, and code documentation with clarity and precision.

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MCQs on Swift Fundamentals

Section 1: Variables and Constants (6 Questions)

1. Which keyword is used to declare a variable in Swift?
   • a) var
   • b) let
   • c) const
   • d) mutable
2. What does the let keyword signify in Swift?
   • a) A variable with no data type
   • b) A constant that cannot be reassigned
   • c) A placeholder for dynamic types
   • d) A mutable variable
3. Which of the following is the correct way to declare a constant in Swift?
   • a) const name = “Swift”
   • b) let name = “Swift”
   • c) static name = “Swift”
   • d) var name = “Swift”
4. What happens if you try to change the value of a constant in Swift?
   • a) It changes dynamically
   • b) It throws a runtime error
   • c) It causes a compile-time error
   • d) It works if the data type is compatible
5. Which statement is true about variables in Swift?
   • a) Variables are immutable by default
   • b) Variables are declared using the var keyword
   • c) Variables cannot store numeric values
   • d) Variables can only store strings
6. How do you declare a variable with an explicit type in Swift?
   • a) var age: Int = 25
   • b) age = Int: 25
   • c) Int var age = 25
   • d) let Int age = 25

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Section 2: Data Types (6 Questions)

7. What type would the number 42 be inferred as in Swift?
   • a) Float
   • b) Double
   • c) Int
   • d) String
8. Which of the following is a valid Swift data type?
   • a) Integer
   • b) Bool
   • c) CharacterArray
   • d) DoubleChar
9. How is a floating-point value represented in Swift?
   • a) Only as a Float
   • b) Only as a Double
   • c) As either Float or Double
   • d) As Int
10. What is the difference between Float and Double in Swift?
    • a) Double has higher precision than Float
    • b) Float can store larger numbers than Double
    • c) They are interchangeable in Swift
    • d) Float is immutable while Double is mutable
11. Which of the following types would store the value true in Swift?
    • a) Bool
    • b) String
    • c) Int
    • d) Character
12. What is the data type of a single character in Swift?
    • a) Char
    • b) String
    • c) Character
    • d) Text

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Section 3: Type Inference and Type Safety (6 Questions)

13. What is type inference in Swift?
    • a) Automatically determining the type of a variable
    • b) Converting one type to another
    • c) Manually defining the type of a variable
    • d) Avoiding type errors at runtime
14. Which statement about type safety in Swift is true?
    • a) Swift enforces strict type checking at runtime
    • b) Swift allows implicit type conversion by default
    • c) Swift ensures type safety during compile-time
    • d) Swift does not support type inference
15. How can you explicitly declare the type of a variable in Swift?
    • a) var name: String = "John"
    • b) let name: String
    • c) Both a and b
    • d) It is not allowed
16. Which of these will cause a type mismatch error in Swift?
    • a) Assigning an Int value to a Float variable
    • b) Assigning a String value to an Int variable
    • c) Assigning a Bool value to a Character variable
    • d) All of the above
17. Why is type safety important in Swift?
    • a) It avoids type-related runtime crashes
    • b) It allows dynamic type conversion
    • c) It makes the code execute faster
    • d) It removes the need for explicit type declarations
18. What is the default type for a floating-point number in Swift?
    • a) Float
    • b) Double
    • c) Decimal
    • d) Int

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Section 4: Comments and Code Documentation (6 Questions)

19. How do you write a single-line comment in Swift?
    • a) /* Comment */
    • b) # Comment
    • c) // Comment
    • d) /// Comment
20. Which of the following is used for multi-line comments in Swift?
    • a) /* Comment */
    • b) // Comment //
    • c) # Comment #
    • d) * Comment *\
21. What are comments used for in Swift code?
    • a) To add additional functionality
    • b) To document code and improve readability
    • c) To execute debug commands
    • d) To identify errors
22. What does the /// comment syntax signify in Swift?
    • a) It marks a multi-line comment
    • b) It is used for documentation comments
    • c) It is a syntax error
    • d) It is equivalent to //
23. Why is code documentation important?
    • a) It improves code readability and maintainability
    • b) It makes the code faster
    • c) It prevents bugs during compilation
    • d) It ensures strict type safety
24. Which tool can generate documentation from Swift comments?
    • a) SwiftLint
    • b) Xcode’s Quick Help
    • c) SwiftDoc
    • d) Both b and c

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Section 5: Miscellaneous Swift Fundamentals (6 Questions)

25. What is the keyword to declare an immutable variable in Swift?
    • a) const
    • b) var
    • c) let
    • d) final
26. How can you print a variable’s value in Swift?
    • a) print("Variable value: \(variable)")
    • b) println(variable)
    • c) echo variable
    • d) print(variable)
27. Which statement is true about Swift’s type system?
    • a) It is dynamic and weakly typed
    • b) It is static and strongly typed
    • c) It is flexible with implicit conversions
    • d) It does not allow explicit type declarations
28. How does Swift handle uninitialized variables?
    • a) It assigns a default value
    • b) It throws a compile-time error
    • c) It leaves them as null
    • d) It converts them to strings
29. What happens if you use an undefined variable in Swift?
    • a) It causes a runtime error
    • b) It causes a compile-time error
    • c) It initializes the variable with a default value
    • d) The code executes normally
30. Which of the following can be used to create a block of reusable code in Swift?
    • a) Function
    • b) Variable
    • c) Constant
    • d) Comment

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Answer Key

Qno	Answer
1	a) var
2	b) A constant that cannot be reassigned
3	b) let name = “Swift”
4	c) It causes a compile-time error
5	b) Variables are declared using the var keyword
6	a) var age: Int = 25
7	c) Int
8	b) Bool
9	c) As either Float or Double
10	a) Double has higher precision than Float
11	a) Bool
12	c) Character
13	a) Automatically determining the type of a variable
14	c) Swift ensures type safety during compile-time
15	c) Both a and b
16	d) All of the above
17	a) It avoids type-related runtime crashes
18	b) Double
19	c) // Comment
20	a) /* Comment */
21	b) To document code and improve readability
22	b) It is used for documentation comments
23	a) It improves code readability and maintainability
24	d) Both b and c
25	c) let
26	a) print("Variable value: \(variable)")
27	b) It is static and strongly typed
28	b) It throws a compile-time error
29	b) It causes a compile-time error
30	a) Function