Module 1

Question 1

What is the difference between multitasking and multithreading?

Answer 1

Multitasking is when several applications seem to run at the same time.
Multithreading is a form of multitasking within an application.

Question 2

What is concurrent programming?

Answer 2

Concurrent programming is to make two or more task seemingly (almost) execute at the same time. (Sharing the computers CPU)

Question 3

What is parallel programming?

Answer 3

Parallel programming is when two or more tasks run exactly at the same time. (Not sharing the computers CPU).

Question 4

What is a process?

Answer 4

An instance of an application being executed.

Question 5

What does a process consist of?

Answer 5

Program instructions to the machine.
Stack memory (call stack) - to keep track of active methods.
A heap memory.
A program counter (register).
Other resources, security information, information about the state of the process etc.

Question 6

Is a process isolated from other processes?

Answer 6

Yes, a process runs in it’s own address space managed by OS and is totally isolated from other processes.

Question 7

What is a thread?

Answer 7

A single sequential flow of control within a program

Question 8

What does all threads within the same process share?

Answer 8

Adress space, code and data

Question 9

What’s the difference between threads and processes?

Answer 9

A process is the execution of a program, isolated from other processes. It runs in its own memory space.
A thread runs within the address space of a process. It is a execution of the whole or parts of a program. Threads share the process memory area.

Question 10

Does every process has a thread?

Answer 10

Yes, every process has at least one thread. More threads can be created in the process.

Question 11

What is concurrency?

Answer 11

A property of a computing system in which several tasks are executing simultaneously. Systems are (or seem to be) progressing at the same time.
Running several programs at the same time is an example.

Question 12

Name two types of concurrency

Answer 12

Multithreading and parallel programming

Question 13

What is a sequential application?

Answer 13

A sequential application has one single thread of execution.

A sequence of statements that are executed one after another.

Question 14

True or false:

A concurrent application has multiple threads of execution.

Answer 14

True

Question 15

True or false:

A sequential application has one single thread of execution.

Answer 15

True

Question 16

How can parallelism be achieved in an application?

Answer 16

By splitting the application into smaller tasks where they can be executed in parallel.

Question 17

Can both concurrency and parallelism be achieved in a single-core CPU?

Answer 17

No, concurrency can but not parallelism.

Question 18

What is the difference between parallelism and concurrency?

Answer 18

Parallelism: Running exactly at the same time. Two applications run purely parallel, each in a separate processor.

Concurrency: Running seemingly at the same time. The processor shares its time to program with so short intervals that it gives the users the illusion of programs running in parallel.

Question 19

True or false:

Parallelism can be considered as a form of concurrency.

Answer 19

True

Question 20

What are the main advantages with multithreading?

Answer 20

Performance and responsiveness.

Question 21

Name some typical thread states.

Answer 21

Ready
Running/active
Blocked/waiting
Terminated

Question 22

What are the two ways to create and start a thread in java?

Answer 22

Provide a Runnable object by implementing the interface Runnable which defines a single method called run.
Subclass the Thread class and override the run method.
In both cases Thread.start() is used to start the thread.

Question 23

What does the Thread.join() method do?

Answer 23

It allows one thread to wait for the completion of another

Question 24

Name some other useful methods in the Thread class

Answer 24

T.isAlive();
T.interrupt();
Thread.currentThread().getName();
Thread.currentThread().getID();

Question 25

What is a foreground thread?

Answer 25

A foreground thread keeps the application alive until it finishes its task. CLR/JVM cannot exit the application when there is a foreground thread running.
Foreground threads are those which keep running even if the main thread is done with its job and ready to exit or terminate.

Question 26

What is a background thread?

Answer 26

A background thread is a thread that runs behind the scenes. For example, a background thread can play music while the application is doing another task.
A background thread is automatically terminated when the application exits even if the thread has not completed its task.

Question 27

True or false:

Every thread has a priority.

Answer 27

True. In java, the threads priority is an integer in the range of 1 to 10 where 1 is the lowest. Thread class defines three types of priorities:
o Minimum priority
o Normal priority
o Maximum priority