বাংলাদেশের কোন অঞ্চলে লবণাক্ততা সমস্যা প্রকট?

Question:

Which of the following statements accurately describes the primary difference between a process and a thread in an operating system?

Options:

    
• A) Threads have their own independent address space, while processes share the address space of the parent program.
    
• B) A process is a lightweight execution unit, whereas a thread is a heavyweight execution unit requiring more overhead.
    
• C) A process represents an independent executing program with its own dedicated memory space, while threads exist within a process and share its memory and resources.
    
• D) Threads cannot be scheduled independently by the operating system kernel, whereas processes can.

Correct Answer: C) A process represents an independent executing program with its own dedicated memory space, while threads exist within a process and share its memory and resources.

Detailed Explanation:

In operating systems, understanding the distinction between processes and threads is fundamental to concurrent programming and resource management:

    
• Process: An instance of a program in execution. It maintains its own isolated memory map (code, data, heap, and stack), file descriptors, and system resources. Communication between processes requires Inter-Process Communication (IPC) mechanisms such as pipes, sockets, or shared memory segments.
    
• Thread: Often called a lightweight process (LWP), a thread is the smallest unit of execution that can be scheduled by an operating system. Multiple threads reside within a single process and share the process's text segment, data segment, and open files, but each thread retains its own program counter, register set, and stack space.

Why Other Options Are Incorrect:

    
• Option A is incorrect: It reverses the roles. Processes have independent address spaces; threads share the memory space of their parent process.
    
• Option B is incorrect: Processes are heavyweight due to dedicated resource allocation and context switching overhead. Threads are lightweight and require significantly less overhead to create and switch between.
    
• Option D is incorrect: Kernel-level threads (which are standard in modern operating systems like Linux and Windows) can be, and routinely are, scheduled independently by the kernel scheduler.