OS Page Replacement Algorithm Optimal

Operating Systems Lab Manual / OS Page Replacement Algorithm Optimal

Program Name	Write C Program for Operating system Page Replacement Algorithm Optimal
Theory	In Optimal pages are replaced in the memory based optimally.
Program	#include<stdio.h> int frames[3], n, m; void framesdisplay(); void main() { int i,j,page[20],framessize[10]; int max,found=0,lg[3],index,k,l,flag1=0,flag2=0,pf=0; float pr; printf("Page Replacement Algorithm - OPTIMAL\n "); printf("Enter length of the reference string: "); scanf("%d",&n); printf("Enter the reference string:"); for(i=0;i<n;i++) scanf("%d",&page[i]); printf("Enter Number of frames:"); scanf("%d",&m); for(i=0;i<m;i++) frames[i]=-1; pf=m; for(j=0;j<n;j++) { flag1=0; flag2=0; for(i=0;i<m;i++) { if(frames[i]==page[j]) { flag1=1; flag2=1; break; } } if(flag1==0) { for(i=0;i<m;i++) { if(frames[i]==-1) { frames[i]=page[j]; flag2=1; break; } } } if(flag2==0) { for(i=0;i<m;i++) lg[i]=0; for(i=0;i<m;i++) { for(k=j+1;k<=n;k++) { if(frames[i]==page[k]) { lg[i]=k-j; break; } } } found=0; for(i=0;i<m;i++) { if(lg[i]==0) { index=i; found = 1; break; } } if(found==0) { max=lg[0]; index=0; for(i=0;i<m;i++) { if(max<lg[i]) { max=lg[i]; index=i; } } } frames[index]=page[j]; pf++; } framesdisplay(); } printf("Number of page faults: %d\n", pf); pr=(float)pf/n*100; printf("Page fault rate = %f \n", pr); } void framesdisplay() { int i; for(i=0;i<m;i++) printf("%d\t",frames[i]); printf("\n"); }
Input	Page Replacement Algorithm - OPTIMAL Enter length of the reference string: 12 Enter the reference string:1 2 3 4 1 2 5 1 2 3 4 5 Enter Number of frames:3
Output	1 -1 -1 1 2 -1 1 2 3 1 2 4 1 2 4 1 2 4 1 2 5 1 2 5 1 2 5 3 2 5 4 2 5 4 2 5 Number of page faults: 7 Page fault rate = 58.333332

Home Back