9.26_optimalpagereplacement.c

/*
 * Name     : Tri Wanda Septian
 * 
 * How to compile the source codes (Linux)
 * $gcc -o a.out a.c
 * 
 *  * 9.26*: Write a program that implements the FIFO, LRU, and optimal page-replacement algorithms presented in this chapter.
 * First, generate a random page-reference string where page numbers range from 0 to 9.
 * Apply the random page-reference string to each algorithm, and record the number of page faults incurred by each algorithm.
 * Implement the replacement algorithm so that the number of page frames can vary from 1 to 7. Assume that demand paging is used.
 */
#include<stdio.h>

int main()
{
    int no_of_frames, no_of_pages, frames[10], pages[30], temp[10], flag1, flag2, flag3, i, j, k, pos, max, faults = 0;
    printf("\nName : Tri Wanda Septian\n");

    printf("Enter number of frames: ");
    scanf("%d", &no_of_frames);

    printf("Enter number of pages: ");
    scanf("%d", &no_of_pages);

    printf("Enter page reference string: ");

    for(i = 0; i < no_of_pages; ++i){
        scanf("%d", &pages[i]);
    }

    for(i = 0; i < no_of_frames; ++i){
        frames[i] = -1;
    }

    for(i = 0; i < no_of_pages; ++i){
        flag1 = flag2 = 0;

        for(j = 0; j < no_of_frames; ++j){
            if(frames[j] == pages[i]){
                flag1 = flag2 = 1;
                break;
            }
        }

        if(flag1 == 0){
            for(j = 0; j < no_of_frames; ++j){
                if(frames[j] == -1){
                    faults++;
                    frames[j] = pages[i];
                    flag2 = 1;
                    break;
                }
            }
        }

        if(flag2 == 0){
            flag3 =0;

            for(j = 0; j < no_of_frames; ++j){
                temp[j] = -1;

                for(k = i + 1; k < no_of_pages; ++k){
                    if(frames[j] == pages[k]){
                        temp[j] = k;
                        break;
                    }
                }
            }

            for(j = 0; j < no_of_frames; ++j){
                if(temp[j] == -1){
                    pos = j;
                    flag3 = 1;
                    break;
                }
            }

            if(flag3 ==0){
                max = temp[0];
                pos = 0;

                for(j = 1; j < no_of_frames; ++j){
                    if(temp[j] > max){
                        max = temp[j];
                        pos = j;
                    }
                }
            }

            frames[pos] = pages[i];
            faults++;
        }

        printf("\n");

        for(j = 0; j < no_of_frames; ++j){
            printf("%d\t", frames[j]);
        }
    }

    printf("\n\nTotal Page Faults = %d", faults);

    return 0;
}