GATE IT 2004 | Question: 14

Question

Which one of the following is NOT shared by the threads of the same process ?

• A. Stack
• B. Address Space
• C. File Descriptor Table
• D. Message Queue

Comments

Threads don't share stack, program counter and registers, shares code, data, heap and files.

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what do they mean by message queue?

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From Tanenbaum:

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Option A

Answer 1

Stack is not shared

Comments

It is true that each thread has it's own stack and program counter. But threads are not independent on each other. Because all threads can access every address in the task, a thread can read or write every other thread's stack.

Taken from Galvin chapter 4(Thread Structure - Para 4)

So can someone please explain if it has anything to do with same or different process?

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No. It can access its own stack

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@Sankaranarayanan P.N can please explain what is message queue?

Answer 2

Threads Share

• Code   
• Data  
• File Descriptor table
• Address spaces 
• Message Queue
• heap
• gloabal varaibles
• accounting information

these things are shared as two threads of the same process are doing same kind of work on different instances and these things don’t get changed while they are doing the task

Threads don’t Share

• Registers
• program counter
• Stack

During performing a task above things get changed so they are not shared by threads

takeaway: Things which will get changed while a task is performed and may affect other task if we use them for other task too cannot be shared.

Answer(A) Stack

Answer 3

Threads have their own stack and registers , although resources like code , data , files and memory is shared.

Answer 4

Stack,program counter and register is not shared by thread.

So A is the answer.

Comments

How is file descriptor table and message queue related to threads??

Answer 5

Explanation of Each Option:

1. Stack:

   • Not shared by threads.
   • Each thread has its own private stack to store function calls, local variables, and return addresses. This separation is necessary to allow independent execution of threads without interfering with each other's function calls and variables.

2. Address Space:

   • Shared by all threads within the same process.
   • Threads share the same memory space, including the code, heap, and global variables.

3. File Descriptor Table:

   • Shared by all threads.
   • Threads can access and modify the same file descriptors, as these are part of the process's shared resources.

4. Message Queue:

   • Shared if implemented within the process's shared memory space.
   • Message queues created for inter-thread communication are typically accessible to all threads within the same process.

correct option is A

 

More on FILE DESCRIPTOR TABLE:
 

The File Descriptor Table is a data structure maintained by the operating system for each process. It tracks open files and I/O resources (e.g., sockets, pipes) associated with a process. This table is crucial for facilitating file operations such as reading, writing, and closing files.