Question

1. An OS is intimately tied to what ? Describe what it is tied to and the components.

2. What is a process
   1. what does it contain
   2. what are its various states
   3. what is contained in a PCB.
   4. Describe what happens when a process is created
3. What is a thread.
   1. What are multi threaded processes ?
   2. What are the benefits of threads. Describe them in detail.
4. Describe the items shared by all threads in a process. What are the items which are private to each thread.
5. On all current computers, at least part of the interrupt handlers are written in assembly language. Why?

Answer 1

1. An operating system is tied to hardware and software. Hardware application deals with the I/O, memory, etc whereas the application program deals with the user end applications.

2. A process is defined as a program which is in execution state. The code written by the end-user converted to binary and when its run in the CPU is called a process.
a. The process has a similar structure as that of memory. It contains a text section for the activity of Program Counter, stack section for the local variable, data section for global variable and heap for dynamic memory.
b. The various states are:
i. New: The Newly created process will have this state.
ii. Ready: When the process is ready for execution. to be picked by the CPU comes in the ready state.
iii. Run: The process that comes from ready to run, which are currently running.
iv. Wait: When the process waits for I/O.
v. Terminate: When the process is executed completely.
vi. Suspended Ready: When the ready queue becomes full, some processes are in waiting.
vii. Suspended block: This occurs when the wait queue becomes full.
c. The process control block contains information related to every process. It includes their priority, their quantum, etc.
d. When a process is created, it is in the new state. It comes to the ready state where it will be picked by the CPU and will execute.

3. A thread is defined as a unit of execution within a single program. The threads present in a process share the memory and resources and can perform concurrently.
a. Multithreaded processes are those processes in which there is more than one thread who are performing concurrently at the same time to execute various tasks
b.
i. With the help of a thread, there is the proper utilization of resources.
ii. Thread minimize the context switching and hence, less time and less effort.
iii. Concurrency is ensured in the process.
4. Threads share the code segment, data segment, and heap segment but not the stack segment.
5. They are written in assembly language because it is easier to write procedures on the basis of different interrupts in assembly language. The higher speed is provided by these functions and assembly language can directly operate on physical CPU.

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