Here is C++ implementation of Shortest Job First (SJF) algorithm.
#include<iostream.h>
#include<conio.h>
struct process
{
int no;
int at;
int et;
int wt;
int tt;
};
void main()
{
clrscr();
process p[4];
int i, j;
for (i = 0; i < 4; i++)
{
cout << "\n Enter arrival time of P" << i + 1 << ":";
cin >> p[i].at;
cout << "\n Enter execution time of P" << i + 1 << ":";
cin >> p[i].et;
p[i].no = i;
}
cout << "\n PNO\tAT\tET";
for (i = 0; i < 4; i++)
{
cout << "\n P" << p[i].no + 1 << "\t" << p[i].at << "\t" << p[i].et;
}
//sorting
process temp;
for (i = 0; i < 4; i++)
{
for (j = i + 1; j < 4; j++)
{
if (p[i].et > p[j].et)
{
temp = p[i];
p[i] = p[j];
p[j] = temp;
}
}
}
p[0].wt = 0;
p[0].tt = p[0].et;
int tte = p[0].et;
for (i = 1; i < 4; i++)
{
p[i].wt = p[i - 1].wt + p[i - 1].et - (p[i].at - p[i - 1].at);
p[i].tt = p[i].wt + p[i].et;
tte = tte + p[i].et;
}
cout << " \n Result";
cout << "\n PNO\tAT\tWT\tET\tTT";
for (i = 0; i < 4; i++)
{
cout << "\n P" << p[i].no + 1 << "\t" << p[i].at << "\t" << p[i].wt << "\t" << p[i].et << "\t" << p[i].tt;
}
cout << "\n Total time:" << tte;
int twt = 0, tat = 0;
for (i = 0; i < 4; i++)
{
twt += p[i].wt;
tat += p[i].tt;
}
float awt = (float) twt / 4;
cout << "\n Average Waiting time:" << awt;
float atat = (float) tat / 4;
cout << "\n Average Turnaround Time:" << atat;
getch();
}
/* Output
Enter arrival time of P1:0
Enter execution time of P1:5
Enter arrival time of P2:0
Enter execution time of P2:3
Enter arrival time of P3:0
Enter execution time of P3:8
Enter arrival time of P4:0
Enter execution time of P4:4
PNO AT ET
P1 0 5
P2 0 3
P3 0 8
P4 0 4
Result
PNO AT WT ET TT
P2 0 0 3 3
P4 0 3 4 7
P1 0 7 5 12
P3 0 12 8 20
Total time:20
Average Waiting time:5.5
Average Turnaround Time:10.5
*/