Process and Thread

Process:
  • An executing instance of a program is called a process.
  • Some operating systems use the term ‘task‘ to refer to a program that is being executed.
  • A process is always stored in the main memory also termed as the primary memory or random access memory.
  • Therefore, a process is termed as an active entity. It disappears if the machine is rebooted.
  • Several process may be associated with a same program.
  • On a multiprocessor system, multiple processes can be executed in parallel.
  • On a uni-processor system, though true parallelism is not achieved, a process scheduling algorithm is applied and the processor is scheduled to execute each process one at a time yielding an illusion of concurrency.
  • Example: Executing multiple instances of the ‘Calculator’ program. Each of the instances are termed as a process.
Thread:
  • A thread is a subset of the process.
  • It is termed as a ‘lightweight process’, since it is similar to a real process but executes within the context of a process and shares the same resources allotted to the process by the kernel
  • Usually, a process has only one thread of control – one set of machine instructions executing at a time.
  • A process may also be made up of multiple threads of execution that execute instructions concurrently.
  • Multiple threads of control can exploit the true parallelism possible on multiprocessor systems.
  • On a uni-processor system, a thread scheduling algorithm is applied and the processor is scheduled to run each thread one at a time.
  • All the threads running within a process share the same address space, file descriptor, stack and other process related attributes.
  • Since the threads of a process share the same memory, synchronizing the access to the shared data withing the process gains unprecedented importance.

Comments

Post a Comment

Please post comments here:-)

Popular posts from this blog

Android Objective type Question and Answers

Android Objective type Question and Answers 1) Once installed on a device, each Android application lives in_______?  a)device memory  b)external memory  c) security sandbox  d)None of the above Ans) c 2)Parent class of Activity?  a)Object  b)Context  c)ActivityGroup  d)ContextThemeWrapper Ans) d 3)What are the Direct subclasses of Activity?  a)AccountAuthenticatorActivity  b) ActivityGroup  c) ExpandableListActivity  d) FragmentActivity  e) ListActivity  f) all the aove Ans) f 4)What are the indirect Direct subclasses of Activity?  a)LauncherActivity  b)PreferenceActivity  c) TabActivity  d)All the above Ans) d 5)Parent class of Service?  a)Object  b)Context  c) ContextWrapper  d)ContextThemeWrapper Ans) c 6)What are the indirect Direct subclasses of Services?  a) RecognitionService  b) RemoteViewsService  c)SpellCheckerService  d)InputMethodService Ans) d 7)Which component is not activated by an Intent?  a)Activity  b)Services  c)Conten
Read more

Android Questions and Answers for written exams

1. bmgr tool is used to a)take backup of the applications b)to restore operations c)wipe archived data for a specific application d)all of the above ans: d 2. foreground service a)starts when you call start foreground() b)may or may not provide a notification for the status bar c)notification can't be dismissed unless the service is either stopped or removed from the foreground d)both a & c ans:d 3. A1,A2,A3 and A4 are activities called using intents.Then A1-A4-A2--A3.A4 calls A2 with intent flag FLAG_ACTIVITY_NO_HISTORY.When finish method is called on A3, What will be the currtent running activity? a)A1 b)A4 c)A3 d)A2 ans: b 4. A1,A2,A3 and A4 are activities called using intents.Then A1-A2-A4--A3.A2 calls A4 with intent flag FLAG_ACTIVITY_CLEAR_TOP.When finish() method is called on A3, what will be the current running activity? a)A4 b)A3 c)A2 d)A1 Ans:  a 5. A1,A2,A3 and A4 are activities called using intents.Then A1-A2-A3-A4. A3 call
Read more

SCJP1.6 Question and Answers

Question – 1 What is the output for the below code ? 1.         public class A { 2.         int add(int i, int j){ 3.                     return i+j; 4.                     } 5.         } 6.         public class B extends A{ 7.         public static void main(String argv[]){ 8.         short s = 9; 9.         System.out.println(add(s,6)); 10.        } 11.        } Options are A. Compile fail due to error on line no 2 B. Compile fail due to error on line no 9 C. Compile fail due to error on line no 8 D. 15 Answer : B is the correct answer. Cannot make a static reference to the non-static method add(int, int) from the type A. The short s is autoboxed correctly, but the add() method cannot be invoked from a static method because add() method is not static. Question – 2 What is the output for the below code ? public class A { int k; boolean istrue; static int p; public void printValue() { System.out.print(k); System.out.print(istrue); System.out.print(p); }
Read more