Merge pull request #36 from hpnightowl/patch-1

Sjf: OS Scheduling algorithm

C++/sjf.cpp

@@ -0,0 +1,81 @@
+/*
+Shortest job first (SJF) or shortest job next, is a scheduling policy that selects the waiting process
+with the smallest execution time to execute next. SJN is a non-preemptive algorithm.
+*/
+
+#include<stdio.h>
+#define N 15 // default size for 15 to init the array to zeros
+int main(){
+    int i,j,k,t,t1,bt[N]={0},at[N]={0},tat[N]={0},wt[N]={0},ct[N]={0};
+	int n,tBT=0,time=0, swap;
+	float sumtat=0,sumwt=0;
+
+    printf("Enter total process: ");
+	scanf("%d",&n);
+
+	for(i=0;i<n;i++){
+		printf("\nEnter Arrival Time for process %d: ",i+1);
+		scanf("%d",&at[i]);
+	}
+	for(int i =0;i<n;i++){
+	    printf("\nBurst Time for process %d: ",i+1);
+	    scanf("%d",&bt[i]);
+	}
+
+	//Sorting based on arrival time
+	for(i=0;i<n;i++){
+        for(j=i+1; j<n; j++){
+            if(at[i] > at[j]){
+                t = at[i];
+                t1 = bt[i];
+                at[i] = at[j];
+                bt[i] = bt[j];
+                at[j] = t;
+               bt[j] = t1;
+            }
+        }
+    }
+
+    k=1;
+    //checking burst time and sorting
+    for(j=0;j<n;j++){
+        time = time + bt[j];
+        t = bt[k];
+        for(i=k;i<n;i++){
+            if(time>=at[i] && bt[i]<t){
+                swap = at[k];
+                at[k] = at[i];
+                at[i] = swap;
+                swap = bt[k];
+                bt[k] = bt[i];
+                bt[i] = swap;
+            }
+        }
+        k++;
+    }
+
+    tBT = at[0];
+    for( j=0;j<n;j++){
+		tBT+=bt[j];
+		ct[j]+=tBT;
+	}
+
+	for(k=0;k<n;k++){
+		tat[k]=ct[k]-at[k];
+		wt[k]=tat[k]-bt[k];
+		sumtat+=tat[k];
+        sumwt+=wt[k];
+	}
+
+	printf("\n\n\t\t\t\t\tSJF\n\n\tArrival Time\tBurst Time\tCompletion Time\tTurn Around Time\tWaiting Time\t\n\n");
+
+	for(i=0;i<n;i++){
+		printf("P%d\t%d\t\t%d\t\t%d\t\t%d\t\t\t%d\n",i+1,at[i],bt[i],ct[i],tat[i],wt[i]);
+	}
+	printf("----------------------------------------------------------------------------------------------------------------");
+	printf("\nTotal\t\t\t\t\t\t\t\t\t\t%.2f\t\t\t\t%.2f\n",sumtat,sumwt);
+
+	printf("\n\nAverage Turnaround Time = %f\n",sumtat/n);
+	printf("Average WT = %f\n\n",sumwt/n);
+  //return 0 for some compliers
+}