Lesson 6: Multi-threading and Concurrent Programming

Question 1

Scheduling algorithms do not determine when to stop one process and give CPU
time to another process. True or false?

Answer 1

False, they DO determine

Question 2

A thread can be created by extending the Thread class, or by implementing the Runnable interface. True or false?

Answer 2

True

Question 3

The process is using the CPU (it has been allocated processor time and the processes machine code is physically executed by the processor.)

Answer 3

Running

Question 4

Transition 2 is usually triggered by a processor interruption signal generated by the corresponding I/O peripheral or a network interface. True or false?

Answer 4

False, Transition 4

Question 5

The use of uni-programming was a feasible solution for the early computers. True or false?

Answer 5

True

Question 6

Current CPU architectures
require less processing units (cores), which increase the parallel processing capacity of the machine. True or false?

Answer 6

False, involve multiple processing units (cores)

Question 7

Less complex and faster than process context switching, making multi-threading an efficient way to emulate parallelism.

Answer 7

Thread context switching

Question 8

A transition is caused by the process scheduler when it decides to give a ready process the chance to run.

Answer 8

Transition 3

Question 9

The process is ready to run (does not have to wait for any event to occur), but it is temporarily stopped

Answer 9

Ready (Runnable)

Question 10

Non-preemptive scheduling usually happens when the currently running process has to switch to the BLOCKED state, while waiting for an external event. True or false?

Answer 10

True

Question 11

In this software approach,
parallel processing requires
that the operating systems
perform fast switching of CPU
between different processes.

Answer 11

Multi-tasking paradigm

Question 12

Thread priorities have to be managed according to the application purpose and requirements. True or false?

Answer 12

True

Question 13

Shortest remaining job first involves giving priority to processes which are about to
finish their operation, leading to a faster de-congestion of the process queue. True or false?

Answer 13

True

Question 14

This method of the Thread class is overridden here to perform the core activity of the tasks.

Answer 14

run()

Question 15

The first process in the queue of READY process will be allocated processor time.

Answer 15

First come–first served

Question 16

When multiple threads exist,
different tasks can be performed in parallel using common data and resources. True or false?

Answer 16

True

Question 17

The solution to the uni-programming problem is represented by the
multi-tasking paradigm. True or false?

Answer 17

False, multi-programming

Question 18

The processes requiring the
shortest time to complete will be given the highest priority.

Answer 18

Shortest remaining job first

Question 19

A thread which manages time-critical tasks should be given lower priority than the other threads. True or false?

Answer 19

False, higher priority

Question 20

Threads may be allocated different priorities
depending on their role within the application process. True or false?

Answer 20

True

Question 21

Transitions 2 and 3 are basically creating an illusion of processing parallelism. True or false?

Answer 21

True

Question 22

Despite the evident benefits multi-threading brings, in terms of application design, the number of threads should be kept to the minimum, in order not to overload the system with non-necessary context switches. True or false?

Answer 22

True

Question 23

A call to this method determines the threads to suspend their execution.

Answer 23

sleep()

Question 24

Emerged as a processor allocation paradigm
where multiple user programs run on the same computer at the same time.

Answer 24

Multi-programming

Question 25

The **READY state** employs a scheduling algorithm to determine the processes which will be allocated processor time and in what order. True or false?

Answer 25

True

Question 26

Mainly determined by the fact that threads own less resources than processes which need to be saved prior to switching the context

Answer 26

Thread switching efficiency

Question 27

The development of personal computers, and the related diversification in application types **determined a definite trend towards widening of user processing requirements**. True or false?

Answer 27

True

Question 28

When multiple processes are in the **RUNNING state**, the operating system must decide which one of them to run first. True or False?

Answer 28

False, READY

Question 29

Threads can **run in preemptive mode** (operating system interrupts thread execution at regular intervals to give processing time to other threads) or in cooperative mode (a thread can access the CPU for as long as it needs). True or false?

Answer 29

True

Question 30

A sequence of a program that performs certain tasks and executes within a process.

Answer 30

Thread

Question 31

A transition occurs when a process cannot continue, as it is waiting for some external event

Answer 31

Transition 1

Question 32

It **creates the illusion of concurrency (parallel execution of user programs) by allocating chunks of processor time to each of the running applications sequentially**.

Answer 32

Multi-tasking

Question 33

Such an example of multi-threading is the **graphical user interface (GUI)** which should be allocated a dedicated thread with a higher priority than other threads. True or false?

Answer 33

True

Question 34

Preemptive scheduling **can be performed according to a scheduling policy**. True or false?

Answer 34

True

Question 35

This can be associated to the thread during its creation and can be changed during the operation of the thread.

Answer 35

Thread priority

Question 36

Scheduling algorithms may do this voluntary (**“non-preemptive scheduling”**)or forced (**“preemptive scheduling”**). True or false?

Answer 36

True

Question 37

Often threads are seen as **heavyweight processes**, as they have their own stack, but share memory and data as well as descriptors of resources with other threads within the same process. True or false?

Answer 37

False, lightweight

Question 38

Threads should be employed when there are clear benefits from using parallel processing only, as involving multi-threading in a highly sequential series of tasks only adds complexity to otherwise a simple solution. True or false?

Answer 38

True

Question 39

It provides another level of parallelism for task execution, with less overhead.

Answer 39

Multi-threading

Question 40

A transition occurs when the external event that the blocked process was waiting for (such as the arrival of some input messages) occurs.

Answer 40

Transition 4

Question 41

First come–first served **treats all the process unequally**, and there is no method to prioritize critical processes. True or false?

Answer 41

False, EQUALLY

Question 42

It is a term used to describe a simple type of operating system design in which a **computer system executes only one program at a time**.

Answer 42

Uni-programming

Question 43

As a result the **threads will be in the BLOCKED state** until the sleep duration of time indicated when sleep() was called **elapses and the threads return to the READY state**. True or false?

Answer 43

True

Question 44

The **run() method** is invoked by the **start() method**, when the thread is started. True or false?

Answer 44

True

Question 45

Processes with higher priority will be allocated processor time more often.

Answer 45

Priority Scheduling

Question 46

Equal processor time slices are assigned to all processes.

Answer 46

Round-robin

Question 47

In a multi-tasking paradigm, as a consequence, at any given time a single process **runs on any multiple processing unit (core)**. True or false?

Answer 47

False, only runs on any one processing unit (core).

Question 48

It involves **only one user program running on any computer at a time.**

Answer 48

Uni-programming

Question 49

The main problem with multi-programming is the **limited number of CPUs (often a single one) the host machine has**. True or false?

Answer 49

True

Question 50

The **process context** includes the process state, an image of the executable machine code corresponding to the program, allocated memory, descriptors of resources used by the process such as file descriptors or handlers, security attributes such as process owner and process permissions, and last, but not least, processor state like content of registers and physical memory addressing. True or false?

Answer 50

True

Question 51

When preemptive scheduling is used, the **currently running process is forced into the READY state** to allow other processes to run. True or false?

Answer 51

True

Question 52

The process is unable to run until some external event occurs (e.g., data is received from the network). CPU could be free during this period if none of the existing processes is in position to run.

Answer 52

Blocked

Question 53

Two implementations of multi-threading:

Answer 53

* Extending Thread class * Implementing Runnable class

Question 54

Is an important feature when critical applications are running on the host machine.

Answer 54

Process priority

Question 55

Application development and deployment has **moved forward and further benefits from the already described processing parallelism** by assigning the same application’s tasks to multiple processes which can individually request CPU time. True or false?

Answer 55

True

Question 56

In general, a **process consists of many threads**, each running at the same time within the process context and performing a unique task. True or false?

Answer 56

True

Question 57

When less important tasks or less time-critical applications run (e.g., operating system updates), they may be allocated **higher priority** in order to minimize the impact on other running applications. True or false?

Answer 57

False, lower

Question 58

It is a running program sequence along with all the resources that its code can affect (also known as process context).

Answer 58

Process

Question 59

It involves the processes giving up processor time willingly to allow other processes to run.

Answer 59

Non-preemptive scheduling

Question 60

A transition is caused by the process scheduler when it decides to temporarily stop the execution of the current process and give another process a chance to run.

Answer 60

Transition 2