可变分区存储管理实验代码实现

以下是可变分区存储管理的实验代码实现，以C语言为例：

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

#define MAX 100

struct block {
    int start;
    int size;
    int status;
};

struct block memory[MAX];

int num;    // 记录内存块数量

void init() {
    // 初始化内存块，将整个内存设为一块
    memory[0].start = 0;
    memory[0].size = MAX;
    memory[0].status = 0;
    num = 1;
}

void display() {
    // 显示内存块的状态
    printf("Memory block status:\n");
    for (int i = 0; i < num; i++) {
        printf("%d\t%d\t%d\n", memory[i].start, memory[i].size, memory[i].status);
    }
}

void allocate(int size) {
    // 分配内存
    int i, j;
    for (i = 0; i < num; i++) {
        if (memory[i].status == 0 && memory[i].size >= size) {
            // 找到第一个空闲块，且大小足够
            memory[i].status = 1;
            if (memory[i].size > size) {
                // 如果空闲块比所需块大，将其分裂
                for (j = num; j > i; j--) {
                    memory[j] = memory[j-1];
                }
                memory[i+1].start = memory[i].start + size;
                memory[i+1].size = memory[i].size - size;
                memory[i+1].status = 0;
                memory[i].size = size;
                num++;
            }
            printf("Allocated %d units at address %d\n", size, memory[i].start);
            break;
        }
    }
    if (i == num) {
        // 没有找到空闲块
        printf("Allocation failed!\n");
    }
}

void free_mem(int start) {
    // 释放内存
    int i;
    for (i = 0; i < num; i++) {
        if (memory[i].start == start && memory[i].status == 1) {
            // 找到要释放的块
            memory[i].status = 0;
            printf("Memory block at address %d is freed.\n", start);
            // 尝试合并相邻空闲块
            if (i > 0 && memory[i-1].status == 0) {
                memory[i-1].size += memory[i].size;
                for (int j = i; j < num-1; j++) {
                    memory[j] = memory[j+1];
                }
                num--;
                i--;
            }
            if (i < num-1 && memory[i+1].status == 0) {
                memory[i].size += memory[i+1].size;
                for (int j = i+1; j < num-1; j++) {
                    memory[j] = memory[j+1];
                }
                num--;
            }
            break;
        }
    }
    if (i == num) {
        // 没有找到要释放的块
        printf("Invalid address or the block has already been freed!\n");
    }
}

int main() {
    int size, choice, start;
    init();
    while (1) {
        printf("1. Allocate memory\n");
        printf("2. Free memory\n");
        printf("3. Display memory blocks\n");
        printf("4. Exit\n");
        printf("Enter your choice: ");
        scanf("%d", &choice);
        switch (choice) {
            case 1:
                printf("Enter the size to allocate: ");
                scanf("%d", &size);
                allocate(size);
                break;
            case 2:
                printf("Enter the start address to free: ");
                scanf("%d", &start);
                free_mem(start);
                break;
            case 3:
                display();
                break;
            case 4:
                exit(0);
            default:
                printf("Invalid choice!\n");
        }
    }
    return 0;
}

这段代码实现了一个简单的可变分区存储管理，可以通过菜单选择进行内存分配、释放和显示内存块状态等操作。其中，初始化函数`init()`将整个内存设为一块；分配函数`allocate()`在空闲块中找到一个大小足够的块进行分配，并在需要时进行分裂；释放函数`free_mem()`释放指定地址的内存块，并尝试合并相邻的空闲块。