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Basic Rust Programming Language MCQ

1. How do you create a Rust project on the command-line?

Cargo new

Rustup init

Cargo start

Rust new-project

Answer

Correct Answer: Cargo new

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2. Generics are useful when you _.

Need to reduce code duplication by concretizing values and restricting parameters in functions

Need to reduce code duplication by abstracting values further, such as in function parameters

Need a supertrait

Are not sure if you need a specific kind of trait

Answer

Correct Answer: Need to reduce code duplication by abstracting values further, such as in function parameters

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3. What is a safe operation on a std::cell:UnsafeCell?

A &mut T reference is allowed. However it may not cpexists with any other references. and may be created only in single-threaded code.

UnsafeCell provides thread-safety. Therefore, creating &T references from multiple threads is safe.

The only safe operation is the .get() method, which returns only a raw pointer.

Non. UnsafeCell only allows code that would otherwise need unsafe blocks to be written in safe code.

Answer

Correct Answer: The only safe operation is the .get() method, which returns only a raw pointer.

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4. What does an underscore (_) indicate when used as pattern?

It matches everything.

It matches underscores.

It matches any value that has a length of 1.

It matches nothing.

Answer

Correct Answer: It matches everything.

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5. Which statement about enums is false?

Enums are useful in matching patterns.

Option is an enum type.

Enum variants can have different types with associated data.

The term enum is short for enummap

Answer

Correct Answer: The term enum is short for enummap

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6. Which choice is not valid loop syntax?

Loop

For

While

Answer

Correct Answer: Do

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7. Your application requires a single copy of some data type T to be held in memory that can be accessed by multiple threads. What is the thread-safe wrapper type?

Mutex>

Rc>

Arc>

Mutex>

Answer

Correct Answer: Arc>

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8. Which types are not allowed within an enum variant's body?

Zero-sized types

Structs

Trait objects

Floating-point numbers

Answer

Correct Answer: Trait objects

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9. What smart pointer is used to allow multiple ownership of a value in various threads?

Arc

Box

Both Arc and Rc are multithread safe.

Answer

Correct Answer: Arc

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10. Which statement about the Clone and Copy traits is false?

Copy is enabled for primitive, built-in types.

Without Copy, Rust applies move semantics to a type's access.

When using Clone, copying data is explicit.

Until a type implements either Copy or Clone, its internal data cannot be copied.

Answer

Correct Answer: Copy is enabled for primitive, built-in types.

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11. When used as a return type, which Rust type plays a similar role to Python's None, JavaScript's null, or the void type in C/C++?

None

Null

()

Answer

Correct Answer: ()

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12. Which statement about lifetimes is false?

Lifetimes were redundantly specified in previous version of Rust.

Lifetimes are specified when a struct is holding a reference to a value.

Lifetimes are specified when certain values must outlive others.

Lifetimes are always inferred by the compiler.

Answer

Correct Answer: Lifetimes are always inferred by the compiler.

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13. Defining a _ requires a lifetime parameter.

Function that ends the lifetime of one of its arguments

Struct that contains a reference to a value

Function with a generic argument

Struct that contains a reference to a boxed value

Answer

Correct Answer: Struct that contains a reference to a value

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14. In matching patterns, values are ignored with _.

.ignore()

An underscore (_)

Skip

Answer

Correct Answer: ..

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15. Which comment syntax is not legal?

//!

Answer

Correct Answer: #

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16. What happens when an error occurs that is being handled by the question mark (?) operator?

The error is reported and execution continues.

An exception is raised. The effect(s) of the exception are defined by the error! macro.

The program panics immediately.

Rust attempts to convert the error to the local function's error type and return it as Result::Err. If that fails, the program panics.

Answer

Correct Answer: Rust attempts to convert the error to the local function's error type and return it as Result::Err. If that fails, the program panics.

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17. The smart pointers Rc and Arc provide reference counting. What is the API for incrementing a reference count?

.add()

.incr()

.clone()

.increment()

Answer

Correct Answer: .clone()

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18. Which is valid syntax for defining an array of i32 values?

Array::with_capacity(10)

[i32]

Array::new(10)

[i32; 10]

Answer

Correct Answer: [i32; 10]

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19. Using the ? operator at the end of an expression is equivalent to _.

A match pattern that branches into True or False

Calling ok_error()

Calling panic!()

A match pattern that may result an early return

Answer

Correct Answer: A match pattern that may result an early return

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20. The term box and related phrases such as boxing a value are often used when relating to memory layout. What does box refer to?

It's creating a pointer on the heap that points to a value on the stack.

It's creating a pointer on the stack that points to a value on the heap.

It's creating a memory guard around values to prevent illegal access.

It's an abstraction that refers to ownership.

Answer

Correct Answer: It's creating a pointer on the stack that points to a value on the heap.

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21. Which cargo command checks a program for error without creating a binary executable?

Cargo --version

Cargo init

Cargo build

Cargo check

Answer

Correct Answer: Cargo check

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22. _ cannot be destructured.

Traits

Tuples

Enums

Structs

Answer

Correct Answer: Traits

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23. Which choice is not a scalar data type?

Integer

Float

Boolean

Tuple

Answer

Correct Answer: Tuple

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24. Which type cast preserves the mathematical value in all cases?

I64 as i32

Usize as u64

I32 as i64

F64 as f32

Answer

Correct Answer: I32 as i64

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25. Which of the following provides the most random seed source for a pseudo random number generator?

C rand() function

/dev/random

Answer

Correct Answer: /dev/random

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26. The purpose of the poll() and select() system calls is to perform which of the following functions?

Watch a set of file descriptors to see which are ready

Frequently check email and other network services

Sample system process information for use by the top command

Answer

Correct Answer: Watch a set of file descriptors to see which are ready

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27. You want to listen on a port for some user-defined data stream. Would you use port 80?

No, it is a 'well-defined' or reserved port.

No, it is best to use three or four digit port numbers.

Yes, it is as good as any other port number.

Yes, it is best to use low numbers for port numbers

Answer

Correct Answer: No, it is best to use three or four digit port numbers.

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28. Race conditions are caused by which of the following conditions in a multi threaded system?

Proper program function requires all threads to run quickly

Proper program function requires that all threads run at the same speed

Proper program function is dependent on the execution sequence and timing of each thread

Answer

Correct Answer: Proper program function is dependent on the execution sequence and timing of each thread

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29. An orphan process occurs as a result of which of the following conditions?

Parent and child process terminate simultaneously

Child process terminates before its parent process

Parent process terminates before its child process

Answer

Correct Answer: Parent process terminates before its child process

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30. When a new process is created using fork(), which of the following describes the state of open file descriptors?

The child inherits the parent’s

The child overwrites the parent’s

The child has distinct copies of the parent’s

The child always has an empty set of closed descriptors

Answer

Correct Answer: The child overwrites the parent’s

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31. Which of the following is correct for the standard file descriptors that are automatically opened in UNIX?

STDIN_FILENO = 0, STDOUT_FILENO = 1, STDERR_FILENO = 2

STDOUT_FILENO = 0, STDERR_FILENO = 1, STDERR_FILENO = 2

STDERR_FILENO = 0, STDOUT_FILENO = 1, STDIN_FILENO = 2

STDIN_FILENO = 0, STDERR_FILENO = 1, STDOUT_FILENO = 2

Answer

Correct Answer: STDOUT_FILENO = 0, STDERR_FILENO = 1, STDERR_FILENO = 2

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32. Which of the following could the fork() command return to the child process?

-1

2054

19456

Answer

Correct Answer: 0

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33. Which of the following techniques can help keep system programs secure?

Encrypt every process’ executable

Setuid important processes to the root user

Limit system calls to administrators

Check all system calls for error conditions

Answer

Correct Answer: Check all system calls for error conditions

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34. The result of calling kill(6003, 0) is which of the following?

Process 6003 terminates

The signal 0 is sent to process 6003

The signal 6003 is sent to process 0

The existence of process 6003 is checked

Answer

Correct Answer: The existence of process 6003 is checked

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35. CORBA's DII allows a client to do which one of the following?

Generate client-side stubs for interfaces

Dynamically link with cross-platform libs

Connect with proxy objects across platforms

Discover new objects and interfaces at runtime

Answer

Correct Answer: Discover new objects and interfaces at runtime

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36. Which of the following is the result of a process calling UNIX exec()?

A new process is created

The process becomes executable

The process is completely overwritten

The process blocks waiting for another process to run

Answer

Correct Answer: The process is completely overwritten

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37. Which of the following best describes the purpose of the unlink() call?

Removes the file from its directory

Sets the file’s Inode count to one (1)

Moves the file in from one directory to another

Answer

Correct Answer: Removes the file from its directory

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38. The ioctl() function is used to interact with which of the following?

Disk Drives

Virtual TTY lines

Special character devices

Answer

Correct Answer: Special character devices

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