Week 2

Question 1

What is a process?

Answer 1

A process is the unit of work in a modern computing system.

Question 2

What are the four sections of a process?

Answer 2

1. Stack - contains temporary data
2. Heap - contains memory which is dynamically allocated during run time
3. Data - contains global variables
4. Text - contains the program code

Question 3

What is the difference between a program and a process?

Answer 3

A program is a passive entity that is stored on a disk where as a process is active and comes from a program when an executable file is loaded into memory. (One program can be several processes)

Question 4

What are the five states of a process as it is executing?

Answer 4

1. New - The process is being created
2. Running - Instructions are being executed
3. Waiting - The process is waiting for some event to occur
4. Ready - The process is waiting to be assigned to a processor
5. Terminated - The process has finished execution

Question 5

What is a PCB?

Answer 5

A process control block (PCB) represents a process and contains many pieces of information relating to that process such as:
- Process state
- Program counter
- CPU registers
- CPU scheduling information
- Memory management information
- Accounting information
- I/O status information

Question 6

What is process scheduling?

Answer 6

Process scheduling is where a process scheduler selects an available process for program execution on a core. Each CPU core can run one process at a time.

Question 7

What are the two different types of scheduling queues?

Answer 7

1. Ready queue - contains all processes residing in main memory waiting to execute
2. Wait queue - contains processes waiting for an event to occur (i.e completion of I/O)

Question 8

What is a context switch?

Answer 8

A context switch is performed when the CPU core needs to switch from one process to another. A save state is performed for the current process and a state restore is performed for a different process. The kernel saves the context of the old process and loads the saved new process scheduled to run

Question 9

What is process creation?

Answer 9

Process creation is where a parent process creates new processes called children processes. Those children processes can than also create new processes. This creates a process tree.

Question 10

What is a thread?

Answer 10

A thread is a segment of a process. A process can have multiple threads and most modern applications are multithreaded.

Question 11

What are the 4 benefits of multithreading?

Answer 11

1. Responsiveness - May allow continued execution if part of process is blocked, especially important for user interfaces
2. Resource Sharing - Threads share resources of process
3. Economy - cheaper than process creation, thread switching lower overhead than context switching
4. Scalability - process can take advantage of multicore architectures

Question 12

What does multicore / multithreaded programming provide?

Answer 12

Multicore and multithreaded programming provides a mechanism for more efficient use of multiple computing cores and provides improved concurrency.

Question 13

What are the two types of parallelism?

Answer 13

Data parallelism - Distributes subsets of the same data across multiple cores, same operation on each

Task parallelism - Distributes threads across cores, each thread performing unique operation

Question 14

What is the difference between concurrency and parrellism?

Answer 14

Concurrency supports more than one task making progress, parallelism implies a system can perform more than one task simultaneously.