用c语言分别使用FIFO、OPT、LRU三种置换算法来 模拟页面置换的过程的代码。其中输入：存储引用串和帧个数的page.txt文档 。输出：页面置换过程中各帧的变化过程

以下是使用FIFO、OPT、LRU三种置换算法来模拟页面置换的C语言代码示例：

FIFO算法：

#include <stdio.h>
#include <stdlib.h>

int main() {
    FILE *fp;
    int pages[1000], frames, page_faults = 0, pointer = 0, frame_list[1000];
    fp = fopen("page.txt", "r");
    if (fp == NULL) {
        printf("File not found!");
        exit(1);
    }
    fscanf(fp, "%d", &frames);
    for (int i = 0; i < frames; i++) {
        frame_list[i] = -1;
    }
    int page_count = 0;
    while (!feof(fp)) {
        fscanf(fp, "%d", &pages[page_count]);
        page_count++;
    }
    fclose(fp);
    for (int i = 0; i < page_count; i++) {
        int page = pages[i];
        int flag = 0;
        for (int j = 0; j < frames; j++) {
            if (frame_list[j] == page) {
                flag = 1;
                break;
            }
        }
        if (flag == 0) {
            frame_list[pointer] = page;
            pointer = (pointer + 1) % frames;
            page_faults++;
        }
        for (int j = 0; j < frames; j++) {
            printf("%d\t", frame_list[j]);
        }
        printf("\n");
    }
    printf("Page Faults = %d", page_faults);
    return 0;
}

OPT算法：

#include <stdio.h>
#include <stdlib.h>

int main() {
    FILE *fp;
    int pages[1000], frames, page_faults = 0, frame_list[1000];
    fp = fopen("page.txt", "r");
    if (fp == NULL) {
        printf("File not found!");
        exit(1);
    }
    fscanf(fp, "%d", &frames);
    for (int i = 0; i < frames; i++) {
        frame_list[i] = -1;
    }
    int page_count = 0;
    while (!feof(fp)) {
        fscanf(fp, "%d", &pages[page_count]);
        page_count++;
    }
    fclose(fp);
    for (int i = 0; i < page_count; i++) {
        int page = pages[i];
        int flag = 0;
        for (int j = 0; j < frames; j++) {
            if (frame_list[j] == page) {
                flag = 1;
                break;
            }
        }
        if (flag == 0) {
            int index = -1, max_distance = -1;
            for (int j = 0; j < frames; j++) {
                int distance = 0;
                for (int k = i + 1; k < page_count; k++) {
                    if (frame_list[j] == pages[k]) {
                        break;
                    }
                    distance++;
                }
                if (distance > max_distance) {
                    max_distance = distance;
                    index = j;
                }
            }
            frame_list[index] = page;
            page_faults++;
        }
        for (int j = 0; j < frames; j++) {
            printf("%d\t", frame_list[j]);
        }
        printf("\n");
    }
    printf("Page Faults = %d", page_faults);
    return 0;
}

LRU算法：

#include <stdio.h>
#include <stdlib.h>

int main() {
    FILE *fp;
    int pages[1000], frames, page_faults = 0, frame_list[1000];
    fp = fopen("page.txt", "r");
    if (fp == NULL) {
        printf("File not found!");
        exit(1);
    }
    fscanf(fp, "%d", &frames);
    for (int i = 0; i < frames; i++) {
        frame_list[i] = -1;
    }
    int page_count = 0;
    while (!feof(fp)) {
        fscanf(fp, "%d", &pages[page_count]);
        page_count++;
    }
    fclose(fp);
    for (int i = 0; i < page_count; i++) {
        int page = pages[i];
        int flag = 0;
        for (int j = 0; j < frames; j++) {
            if (frame_list[j] == page) {
                flag = 1;
                break;
            }
        }
        if (flag == 0) {
            int lru_index = -1;
            for (int j = 0; j < frames; j++) {
                if (frame_list[j] == -1) {
                    lru_index = j;
                    break;
                }
                if (pages[i + 1] == frame_list[j]) {
                    lru_index = j;
                    break;
                }
                if (lru_index == -1 || pages[i + 1] == -1) {
                    lru_index = j;
                } else {
                    int count1 = 0, count2 = 0;
                    for (int k = i - 1; k >= 0; k--) {
                        if (pages[k] == frame_list[j] && count1 == 0) {
                            count1++;
                        }
                        if (pages[k] == frame_list[lru_index] && count2 == 0) {
                            count2++;
                        }
                        if (count1 > 0 && count2 > 0) {
                            break;
                        }
                    }
                    if (count1 == 0) {
                        lru_index = j;
                    }
                }
            }
            frame_list[lru_index] = page;
            page_faults++;
        }
        for (int j = 0; j < frames; j++) {
            printf("%d\t", frame_list[j]);
        }
        printf("\n");
    }
    printf("Page Faults = %d", page_faults);
    return 0;
}

以上代码中，假设page.txt文件中第一个数为帧数，后面的数为存储引用串。每次页面置换后，都会输出当前帧中各页面的编号，最后输出页面缺页次数。