Assignment 02: Process Concepts and the Process Control Block

Self-Assessment

Instructions: Answer the following questions concisely. For analytical and calculation questions, ensure you justify your reasoning based on operating system principles.

Part A: Process Fundamentals and Memory Layout

1. Process Definition: Differentiate a “program” from a “process” and explain why a process is considered an “active entity.”

2. Memory Segments: A process is divided into multiple memory segments. Briefly describe the contents of the following segments:

• Text Segment
• Data Segment (Initialized and Uninitialized/BSS)
• Heap
• Stack

Part B: Process States and Transitions

1. State Identification: Define the exact condition of a process in the following states:

• Ready
• Waiting (Blocked)
• Terminated

2. State Transitions: Explain the specific OS events that trigger the following state transitions:

• Running $\rightarrow$ Ready
• Running $\rightarrow$ Waiting

Part C: The Process Control Block (PCB) and Context Switching

1. PCB Anatomy: The Process Control Block is the OS’s comprehensive “identity card” for each active process. List at least four specific categories of information stored within a PCB.

2. Context Switching Mechanism: Detail the three distinct phases of a context switch.

3. The Overhead Dilemma: Why is a context switch considered “pure overhead” from the perspective of user processes?

Part D: Special Process Types and Kernel Interfaces

1. Zombie vs. Orphan: Explain the fundamental difference between a Zombie process and an Orphan process. Why is a large accumulation of Zombie processes a serious system concern?

2. The /proc Filesystem: The /proc filesystem provides a virtual interface to kernel data structures. If you query /proc/PID/status for a specific process, what do the fields VmSize and VmRSS represent regarding resource usage?

Part E: Advanced Synthesis & Application (Exam Preparation)

Exercise 1: Context Switching Performance Calculations Assume an operating system performs a context switch that takes exactly $10 \mu s$ (microseconds) to execute. The CPU scheduler is configured with a time slice of $10 ms$ (milliseconds).

• Task: If all processes always utilize their full time slice, calculate the percentage of CPU time spent entirely on context switching overhead. Show your calculation.

Exercise 2: PCB State Mapping For the following scenario, identify the most likely process state transition and the specific PCB fields that the operating system must actively update.

• Scenario: An executing background compilation task is preempted because the OS timer interrupt fires, signaling the end of its allocated time slice.