三种页面置换算法c语言代码

页面置换算法是一种内存管理算法，常用于虚拟内存系统中。常见的三种页面置换算法包括FIFO算法、最优算法（OPT）和最近最久未使用算法（LRU）。以下是三种算法的C语言代码实现。

1. FIFO算法

#include <stdio.h>

int main()
{
    int pages[100], frames[10], pageNum, frameNum, faults=0, j, k, l, flag;

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

    printf("Enter the page reference string: ");
    for(j=0; j<pageNum; j++)
        scanf("%d", &pages[j]);

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

    for(j=0; j<frameNum; j++)
        frames[j] = -1;

    j = 0;
    printf("\nReference String\t Page Frames\n");
    for(k=0; k<pageNum; k++)
    {
        printf("%d\t\t", pages[k]);
        flag = 0;
        for(l=0; l<frameNum; l++)
        {
            if(frames[l] == pages[k])
            {
                flag = 1;
                break;
            }
        }
        if(flag == 0)
        {
            frames[j] = pages[k];
            j = (j+1)%frameNum;
            faults++;
            for(l=0; l<frameNum; l++)
                printf("%d\t", frames[l]);
        }
        printf("\n");
    }
    printf("\nTotal Page Faults: %d", faults);

    return 0;
}

2. 最优算法（OPT）

#include <stdio.h>
#include <limits.h>

int main()
{
    int pages[100], frames[10], pageNum, frameNum, faults=0, j, k, l, m, max, flag;

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

    printf("Enter the page reference string: ");
    for(j=0; j<pageNum; j++)
        scanf("%d", &pages[j]);

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

    for(j=0; j<frameNum; j++)
        frames[j] = -1;

    printf("\nReference String\t Page Frames\n");
    for(k=0; k<pageNum; k++)
    {
        flag = 0;
        for(l=0; l<frameNum; l++)
        {
            if(frames[l] == pages[k])
            {
                flag = 1;
                break;
            }
        }
        if(flag == 0)
        {
            max = INT_MIN;
            for(l=0; l<frameNum; l++)
            {
                flag = 0;
                for(m=k+1; m<pageNum; m++)
                {
                    if(frames[l] == pages[m])
                    {
                        flag = 1;
                        break;
                    }
                }
                if(flag == 0 && pages[m] != -1 && max < m)
                {
                    max = m;
                    j = l;
                }
            }
            frames[j] = pages[k];
            faults++;
            printf("%d\t\t", pages[k]);
            for(l=0; l<frameNum; l++)
                printf("%d\t", frames[l]);
            printf("\n");
        }
    }
    printf("\nTotal Page Faults: %d", faults);

    return 0;
}

3. 最近最久未使用算法（LRU）

#include <stdio.h>

int main()
{
    int pages[100], frames[10], pageNum, frameNum, faults=0, j, k, l, m, min, flag[10], counter=0;

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

    printf("Enter the page reference string: ");
    for(j=0; j<pageNum; j++)
        scanf("%d", &pages[j]);

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

    for(j=0; j<frameNum; j++)
        frames[j] = -1;

    printf("\nReference String\t Page Frames\n");
    for(k=0; k<pageNum; k++)
    {
        flag[k] = 0;
        for(l=0; l<frameNum; l++)
        {
            if(frames[l] == pages[k])
            {
                flag[k] = 1;
                break;
            }
        }
        if(flag[k] == 1)
        {
            counter++;
            continue;
        }
        if(counter < frameNum)
        {
            frames[counter] = pages[k];
            counter++;
        }
        else
        {
            min = 9999;
            for(l=0; l<frameNum; l++)
            {
                if(flag[l] < min)
                {
                    min = flag[l];
                    j = l;
                }
            }
            frames[j] = pages[k];
            faults++;
        }
        printf("%d\t\t", pages[k]);
        for(l=0; l<frameNum; l++)
            printf("%d\t", frames[l]);
        printf("\n");
        for(l=0; l<frameNum; l++)
            flag[l]++;
    }
    printf("\nTotal Page Faults: %d", faults);

    return 0;
}