Shortest Job First Scheduling Algorithm (Operating Systems)

Shortest Job First Scheduling Algorithm (Operating Systems)

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Description: Following C code runs a simulation to show how process scheduling in operating system is done using the job scheduling algorithm Shortest Job First. SJF is one of the many scheduling algorithms in operating system.

#include<stdio.h>

#include<unistd.h>

#include<stdlib.h>

#include<errno.h>

#include<string.h>

#include<sys/types.h>

struct Node{

   int p_id;

   int arr_time;

   int exe_time;

};

int main(){

   int i,j,min,counter=100,no_of_processes;

   struct Node *Queue,temp;

   printf("\n--> Shortest Job First Scheduling <--\n");

   printf("Enter no. of Processes:");

   scanf("%d",&no_of_processes);

   Queue=malloc(no_of_processes);

   for(i=0;i<no_of_processes;i++){

      printf("Give Process#%d id :\n",i+1);

      scanf("%d",&Queue[i].p_id);

      printf("Give Arrival Time (0~23):\n");

      scanf("%d",&Queue[i].arr_time);

      printf("Give Execution Time (in secs.):\n");

      scanf("%d",&Queue[i].exe_time);

   }

   counter=0;

   for(i=0;i<no_of_processes-1;i++){

      min=i;

      for(j=i+1;j<no_of_processes;j++)

          if(Queue[j].exe_time<Queue[min].exe_time && Queue[j].arr_time<=counter)

             min=j;

      counter=counter+Queue[min].exe_time;

      temp=Queue[i];

      Queue[i]=Queue[min];

      Queue[min]=temp;

   }

   for(i=0;i<no_of_processes;i++){

      printf("\t--> PROCESS with Process ID#%d <--\n",Queue[i].p_id);

      
      printf("This process arrived at %d and requires %d seconds for execution\n\n",Queue[i].arr_time,Queue[i].exe_time);

      
      printf("Execution in Progress\n\n");

      for(j=0;j<Queue[i].exe_time;j++){

          sleep(1);

          printf("*");

         

      }

      printf("\n\nPROCESS FINISHED\n\n");

   }

        return 0;
}