Day 01Part 08- Operating system lecture for gate for computer science – Attributes of Processes.

Day 01Part 08- Operating system lecture for gate for computer science – Attributes of Processes.

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 Attributes of Processes – Operating System (GATE CS Lecture)

A process in an Operating System (OS) is an instance of a program in execution. Every process has certain attributes that help the OS manage and schedule it efficiently.

 What is a Process?

A process is a program in execution, consisting of:
Program Code (Text Section) – The instructions to be executed.
Program Counter (PC) – Stores the next instruction to execute.
Stack – Contains function calls, return addresses, and local variables.
Heap – Dynamic memory allocation (e.g., malloc in C).
Data Section – Global variables and static data.

 Attributes of a Process

Each process has a unique set of attributes stored in the Process Control Block (PCB).

1. Process ID (PID)

• A unique identifier assigned to each process.
• Used by the OS to track and manage processes.

2. Process State

A process can be in one of the following states:
New – Process is being created.
Ready – Waiting for CPU time.
Running – Currently executing on the CPU.
Waiting (Blocked) – Waiting for I/O or other resources.
Terminated – Process has finished execution.

Example: If a process is waiting for input from the keyboard, it moves to the Waiting state.

3. Program Counter (PC)

• Holds the memory address of the next instruction to execute.
• OS uses it to resume a process after an interruption.

4. CPU Registers

• Includes: General-purpose registers, stack pointers, and flags.
• These store temporary data needed for execution.
• OS saves and restores registers during context switching.

5. Memory Management Information

• Defines how the process interacts with RAM.
• Includes:
  Base and Limit Registers – Define memory boundaries.
  Page Tables – Used in virtual memory systems.
  Segment Tables – Used in segmentation memory management.

Example: If a process tries to access memory outside its boundary, the OS generates a segmentation fault.

6. Accounting Information

• Stores process statistics like:
   CPU usage 
   Execution time 
  Process priority 
   Number of I/O operations performed

Example: The OS uses this data for scheduling and billing in time-sharing systems.

7. I/O Status Information

• Tracks the files and devices used by the process.
• Includes:
   List of open files 
   I/O device usage
•  Network connections

Example: If a process is reading a file, it stays in the Waiting state until I/O is complete.

 Process Control Block (PCB)

All process attributes are stored in a data structure called the Process Control Block (PCB).

Attribute	Description
Process ID (PID)	Unique identifier for the process
Process State	New, Ready, Running, Waiting, Terminated
Program Counter	Address of the next instruction
CPU Registers	Store temporary process data
Memory Management Info	Page tables, base & limit registers
Accounting Info	CPU time, priority, execution history
I/O Info	Files and devices used by the process

The PCB is crucial for context switching between processes!

 Summary

 Every process has attributes stored in the Process Control Block (PCB).
 Key attributes include PID, Process State, Program Counter, CPU Registers, and Memory Information.
 The OS uses these attributes for scheduling, execution, and memory management.

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Day 01Part 08- Operating system lecture for gate for computer science – Attributes of Processes.

OPERATING SYSTEMS LECTURE NOTES …

OPERATING SYSTEM

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