Note: Click on the 'start' button in the control panel to start the simulation.

ROTATE the screen to landscape

Controls

Current Process:

Current subsystem:

Subsystem instructions

Interrupt Handlers

Displays

CPU

Dialog

📋 Click the "Start" button in the 'Controls' section.
Our objective in this experiment is to understand the mechanism of context switching used by the OS for multi processing. In this simulation, we approach the context switching technique at a three level abstraction (User, Hardware and Kernel)

What is context?
A process context refers to the current execution state and information associated with a running process in an operating system. It represents a snapshot of the process's execution at a particular point in time.
Process context can change dynamically while the process is executing on the CPU.

What is PCB?:
In order to virtualize the execution of a process, the OS needs to have an internal account of the state of a process. This representation of the state of a process is stored in memory as a Process Control Block(PCB).
The PCB is used primarily during context switches, but it doesn't actively reflect the process's changing context while it's running. Instead, the changing process context is stored in various CPU registers and memory locations, not within the PCB.

Program A: Simple addition program 


#include 
int main()
{
    int a, b, c;
    a = 5;
    b = 10;
    c = a + b;
    return c;
}

Program B: Read and add program 


#include 
int main()
{
    int a, b, c;
    a = 15;
    scanf("%d", &b); 
    c = a + b;
    return c;
}



Here are few commands that will help you understand the context switching in linux OS. 


$ grep ctxt /proc/$pid/status
The above command will give you the number of context switches that have happened for the process with the given pid. You can get the pid of a process using the following command. 

$ htop
Another good way to inspect a process on your system is using the vmstat command. This will give you a detailed overview of the number of context switches, number of interrupts, and further information like the cache used etc.



TODO...