Shortest Job First Algorithm

harshchandra

This code calculates and the average waiting time of the process given acc to their burst time..It is a famous scheduling algorithm for process scheduling in operating sysytem . After calculating waiting time it also generates the gantt chart for the process given .

jephthah commented: thanks for the effort, but the code sucks. since it can't be compiled on a standard C compiler, who knows if it's even correct. -1
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About the Author

Student Of B.Tech

//////////////////////////////////////////////////////
///////      SHORTEST JOB FIRST ALGORITHM     ///////
////////////////////////////////////////////////////

/* Developed BY : Harsh Chandra
   Contact : harshchandra@gmail.com
   Tested & Compiled on Turbo C++ IDE
*/



# include<stdio.h>
# include<conio.h>
# include<alloc.h>

struct node
{  int process_no;
   int btime;
   struct node *link;
};

void append(struct node **,int,int);
void display(struct node *,int);
void chart(struct node **);

void main()
{  clrscr();
   struct node *p;
   p = NULL; /* Empty Linked list */
   int i=1,time;
   char ans = 'y';
   while(ans != 'n')
   {    printf("\nEnter Burst Time For Process No. %d : ",i);
	scanf("%d",&time);
	append(&p,i,time);
	printf("Any More Process (Y/N) ? ");
	ans = getche();
	i++;
   }
   getch();
   clrscr();
   printf("\nThe Order Of Execution Of Process For SJF Algorithm Will be :- ");
   display(p,1);
   getch();
   printf("\nThe Waiting Time Of Process For SJF Algorithm Will be :- ");
   display(p,2);
   getch();
   chart(&p);
   getch();

}

void append(struct node **q,int i,int time)
{  struct node *r,*temp = *q;
   r = (struct node *)malloc(sizeof(struct node));
   r->process_no = i;
   r->btime = time;

   /* If list is empty or new data to be inserted b4 the first node */
   if(*q==NULL || (*q)->btime > time)
   {   *q = r;
      (*q)->link = temp;
   }
   else
   {  /* traverse the entire linked list
      to search the position the new node to be inserted */
      while(temp != NULL)
      {   if(temp->btime <=time &&(temp->link->btime > time || temp->link ==NULL))
	  {   r->link = temp->link;
	      temp->link = r;
	      r->link = NULL;
	  }
	  temp = temp->link;
      }
   }
}

void display(struct node *q,int kk)
{   struct node *temp;
    int wtime,avg=0,total = 0,count=0;
    temp = q;
    int i;
    printf("\n");
    printf("\n\t\t%c",218);
    for(i=1;i<33;i++)
    { if(i==17)
      printf("%c",194);
      else
      printf("%c",196);
    }
    printf("%c",191);
    if(kk==1)
    { printf("\n\t\t%c  PROCESS NO.   %c  BURST TIME   %c\n",179,179,179);
    }
    if(kk==2)
    { printf("\n\t\t%c  PROCESS NO.   %c  WAIT  TIME   %c\n",179,179,179);
    }
    printf("\t\t%c",195);
    for(i=1;i<33;i++)
    { if(i==17)
      printf("%c",197);
      else
      printf("%c",196);
    }
    printf("%c",180);

    while( temp !=NULL)
    {  count++;
       if(kk==1)
       {    printf("\n\t\t%c      %d.        %c      %3d      %c",179,temp->process_no,179,temp->btime,179);
       }
       if(kk==2)
       {  if(temp ==q)  /* First Process In The Ready Queue */
	  {  wtime = 0;
	     total+= temp->btime;
	     avg+=wtime;
	  }
	  else
	  {  wtime = total;
	     total+= temp->btime;
	     avg +=wtime;
	  }

	  printf("\n\t\t%c      %d.        %c      %3d      %c",179,temp->process_no,179,wtime,179);

	}
	temp=temp->link;
    }
    printf("\n\t\t%c",192);
    for(i=1;i<33;i++)
    { if(i==17)
      printf("%c",193);
      else
      printf("%c",196);
    }
    printf("%c",217);
    if(kk==2)
    {  printf("\nThe Average Waiting Time (%d %c %d) = %.2f",avg,246,count,float(avg/float(count)));
    }

}

void chart(struct node **q)
{
    printf("\n");
    printf("\nThe Glant Chart Is As Follows :-\n");

    struct node *temp,*temp1,*temp2,*temp3,*temp4;
    temp = *q; temp1 = *q;temp2 = *q;temp3 = *q;temp4=*q;
    int sum = 0;float sfactor;
    while(temp4 !=NULL)
    {  sum+=temp4->btime;
       temp4 = temp4->link;
    }
    if(sum<80)
    {  sfactor = 1.0;
    }
    else
    { sfactor = (sum%80)/float(sum);
    }

    int i,k=0;
    printf("%d",k);
    while(temp3 != NULL)
    {   if((sfactor*temp3->btime) == 0)
	{  goto harsh;
	}
	for(i=-1;i<=(sfactor*temp3->btime);i++)
	{   printf(" ");
	}
	k+=temp3->btime;
	printf("%d",k);
	harsh:
	temp3=temp3->link;
    }
    printf("\n");
    while( temp !=NULL)
    {   if(temp == *q)
	{
	    printf("%c%c",218,196);
	    if((sfactor*temp->btime) == 0)
	    {   goto last;
	    }

	    for(i=-1;i<=(sfactor*temp->btime);i++)
	    {  printf("%c",196);
	    }
	    if(temp->link != NULL)
	    {  printf("%c",194);
	    }
	    else
	    {  printf("%c",191);
	    }
	}
	else
	{   if((sfactor*temp->btime) == 0)
	    {  goto last;
	    }
	    for(i=-1;i<=(sfactor*temp->btime);i++)
	    {   printf("%c",196);
	    }
	    if(temp->link != NULL)
	    {  printf("%c",194);
	    }
	    else
	    {  printf("%c",191);
	    }
	}
	last:
	temp = temp->link;

    }
    printf("\n");
    printf("%c ",179);

    while(temp1 != NULL)
    {     if((sfactor*temp1->btime) == 0)
	    {  goto last1;
	    }
	  for(i=0;i<=(sfactor*temp1->btime);i++)
	  {  if(i==int(sfactor*temp1->btime)/2)
	     {  printf("P%d",temp1->process_no);
	     }
	     else
	     printf(" ");
	  }
	  printf("%c",179);
	  last1:
	  temp1 = temp1->link;

    }

    printf("\n");
    while(temp2 !=NULL)
    {  if(temp2 == *q)
       {    printf("%c%c",192,196);
	    if((sfactor*temp2->btime) == 0)
	    {  goto last2;
	    }
	    for(i=-1;i<=(sfactor*temp2->btime);i++)
	    {  printf("%c",196);
	    }
	    if(temp2->link != NULL)
	    {  printf("%c",193);
	    }
	    else
	    {  printf("%c",217);
	    }
       }
       else
       {   if((sfactor*temp2->btime) == 0)
	    {  goto last2;
	    }
	   for(i=-1;i<=(sfactor*temp2->btime);i++)
	   {  printf("%c",196);
	   }
	   if(temp2->link != NULL)
	    {  printf("%c",193);
	    }
	    else
	    {  printf("%c",217);
	    }
       }
      last2:
      temp2=temp2->link;

    }
}
manutd 2 Junior Poster

1) This void main() Should be int main( void )
2)Try to eliminate the nonstandard functions.

kadom -2 Newbie Poster

very good code and thanks very much

WaltP commented: Why are you resurrecting a 4 year old post with a worthles (and wrong) reply? -2
WaltP 2,905 Posting Sage w/ dash of thyme Team Colleague

Actually, it's very bad code, as manutd points out.
1) Illegal form of main() used
2) Made with a compiler at least 25 years old
3) Using functions that don't exist in today's compilers
4) Using headers that don't exist in most compilers
5) No comments make the code completely useless as a teaching tool

IMO, this does not qualify as a CODE Snippet.

It is nicely formatted though, but the indenting needs to be a tad more consistent.

maxx123f -1 Newbie Poster

its working on TurboC..but the graping i think is not right...

but thank you very much...
now i can pass my project...
lol

jephthah commented: if you pass your project with crap code littered with goto's, you go to a sad sad school. god help any companies who hire you people. -1
jephthah 1,888 Posting Maven

conio.h, check. alloc.h, check. goto, che ... wait, what?

GOTO?

is this a joke?

where do you people come from?

angie0406 0 Newbie Poster

como se hacen los encabezados para este codigo

ezkonekgal -1 Junior Poster

hello.. i want to run this program and see how it is.. I'm using bloodshed dev c++.. it doesnt recognize malloc and clrscr... pls someone help.. ??

ezkonekgal -1 Junior Poster

and by the way.. is this non preemptive SJF?

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