C program for FIFO page replacement algorithm

Introduction to FIFO page replacement :

                       The simplest page-replacement algorithm is a first-in,first-out(FIFO)algorithm. A FIFO replacement algorithm associates with each page the time when that page was brought into memory. When a page must be replaced, the oldest page is chosen. Notice that it is not strictly necessary to record the time when a page is brought in. We can create a FIFO queue to hold all pages in memory. We replace the page at the head of the queue. When a page is brought into memory, we insert it at the tail of the queue.


C program for FIFO page replacement :

#include<stdio.h>

int main()

{

            int i,j,n,page[50],frameno,frame[10],move=0,flag,count=0;

            float rate;

            printf("Enter the number of pages\n");

            scanf("%d",&n);

            printf("Enter the page reference numbers\n");

            for(i=0;i<n;i++)

            scanf("%d",&page[i]);

            printf("Enter the number of frames\n");

            scanf("%d",&frameno);

            for(i=0;i<frameno;i++)

            frame[i]=-1;

            printf("Page reference string\tFrames\n");

            for(i=0;i<n;i++)

            {

                        printf("%d\t\t\t",page[i]);

                        flag=0;

                        for(j=0;j<frameno;j++)

                        {

                                    if(page[i]==frame[j])

                                    {

                                                flag=1;

                                                printf("No replacement\n");

                                                break;

                                    }

                        }

                        if(flag==0)

                        {

                                    frame[move]=page[i];

                                    move=(move+1)%frameno;

                                    count++;

                                    for(j=0;j<frameno;j++)

                                    printf("%d\t",frame[j]);

                                    printf("\n");

                        }

            }

            rate=(float)count/(float)n;

            printf("Number of page faults is %d\n",count);

            printf("Fault rate is %f\n",rate);

            return 0;

}

OUTPUT :