Question

Please briefly explain the answer and why.

(1) What are the differences between a process and a thread? Explain in perspectives of memory sharing, switching, communication, etc.

(2) In inter-process communication using message passing, there are two types of send/receive operations: blocking send/receive and non-blocking send/receive. What is the difference between the two approaches? Explain how the operations will behave when called.

(3) When a process is created, memory is allocated for the process. Describe each section of the memory allocated to the process, and what goes into each section.

Answer 1

Ans-(1)Definition-A process is a program under execution i.e an active program and a thread is a lightweight process that can be managed independently by a scheduler.

a)Memory Sharing-A process has its own address space where as a thread uses the process’s address space and shares it with the other threads of that process.

b)Context switching time-Processes require more time for context switching as they are heavier on the other hand Threads require less time for context switching as they are lighter than processes.

c)Communication-Communication between processes requires more time than between threads but Communication between threads requires less time than between processes.

d)Resource Consumption-Processes require more resources than threads but Threads generally need less resources than processes.

Ans-(2)Interprocess Communication-

Interprocess communication refers to the exchange of information between separate threads or processes. There are two basic models of interprocess communication. Information can be exchanged by utilising a shared region of memory between the communicating parties or by using explicit message passing primitives.

The message passing operations Send and Receive may be either blocking or non-blocking.

Blocking Send:  Sending process is blocked until the message passing mechanism has delivered the message to the receiving process or to a mailbox.

Non-Blocking Send: The sending process sends a message and can continue other tasks immediately while the message passing mechanism delivers the message.

Blocking Receive: Receiver waits until a message is received by it.

Non-Blocking Receive:   Receiver either gets an available message or a null value returned by the Receive primitive.

Ans-(3) When a program is loaded into the memory and it becomes a process, it can be divided into four sections ─ stack, heap, text and data. The attached image shows a simplified layout of a process inside main memory .

Component & Description:

Stack-The process Stack contains the temporary data such as method/function parameters, return address and local variables.

Heap-This is dynamically allocated memory to a process during its run time.

Text-This includes the current activity represented by the value of Program Counter and the contents of the processor's registers.

Data-This section contains the global and static variables.