操作系统之——页面置换算法C语言实现

// 页面置换算法.cpp : 定义控制台应用程序的入口点。//#include "stdafx.h"#include "stdlib.h"#include "stdio.h"#include "time.h"#include "string.h"#define MEMORY_BLOCKS 20//内存物理总块数#define PROGRAM_PAGES 50//程序分页数上限#define PAGE_USE_LONGTH 100//页面走向长度最大值#define FIFO 1//先进先出置换#define LRU 2//最久未用置换int memory_blocks=0;//分配内存物理块数int program_pages=0;//程序分页数int memory_allocation[MEMORY_BLOCKS];//内存分配情况struct VISIT {//访问字段int load_time;//装载时间int frequency;//使用频率的顺序，0为最高};struct PAGR_LIST {//页表int page_num;//页号int block_num;//物理块号bool state;//状态位bool modify;//修改位struct VISIT visit;//访问字段int disk;//外存地址}page_list[PROGRAM_PAGES];int create_rand(int a, int b);void init(int m, int p);void page_adjust(int p);bool allocation_once(int p, int f);int change_page(int f);void huanhang(int l);void show_me();void simulation(int l, int f);void menu();int create_rand(int a, int b) {//生成随机数int r;r = rand() % (b - a+1) + a;//printf("%d",r);return r;}void init(int m,int p) {memory_blocks = m;program_pages = p;for (int i = 0; i < memory_blocks ; i++) {memory_allocation[i] = -1;}for (int i = 0; i < program_pages ; i++) {page_list[i].page_num = i;page_list[i].block_num = -1;page_list[i].state = false;page_list[i].modify = false;page_list[i].visit.load_time = 0;page_list[i].visit.frequency = -1;}printf("\n初始化完成\n");}void page_adjust(int p) {//内存中其他页的调整for (int i = 0; i <program_pages; i++) {if (page_list[i].state == true) {//内存中的页page_list[i].visit.load_time += 1;if (page_list[p].visit.frequency == -1) {//该页不在内存page_list[i].visit.frequency += 1;}else {//该页在内存if (page_list[i].visit.frequency < page_list[p].visit.frequency) {page_list[i].visit.frequency += 1;}}}}}bool allocation_once(int p,int f){//单次访问 p为要访问的页，f为置换算法bool reg = false;//访问成功的标记if (page_list[p].state == false) {//该页未在内存中for (int i = 0; i < memory_blocks; i++) {if (memory_allocation[i] == -1) {//有内存块可供分配reg = true;page_adjust(p);//调整当前顺序memory_allocation[i] = p;page_list[p].block_num = i;page_list[p].state = true;page_list[p].visit.load_time += 1;page_list[p].visit.frequency = 0;break;}}}else {//该页已在内存中reg = true;page_adjust(p);page_list[p].visit.frequency = 0;}if (reg == false) {//需要置换change_page(f);}return reg;}int change_page(int f) {//页面置换算法int out = -1;//被换出的页号int block = -1;//空出的物理块号if (f == FIFO) {for (int i = 0; i < memory_blocks; i++) {if (page_list[memory_allocation[i]].visit.load_time > out) {out = page_list[memory_allocation[i]].visit.load_time;block = i;}}out = memory_allocation[block];}else if(f == LRU){for (int i = 0; i < memory_blocks; i++) {if (page_list[memory_allocation[i]].visit.frequency == memory_blocks-1) {block = i;break;}}out= memory_allocation[block];}//收尾操作memory_allocation[block] = -1;page_list[out].block_num = -1;page_list[out].state = false;page_list[out].visit.load_time = 0;page_list[out].visit.frequency = -1;return out;}void huanhang(int l){//换行（页表显示用）printf("\n+--------");for (int i = 0; i<l; i++)printf("-----");printf("+\n");}void show_me() {//页表显示if (memory_blocks != 0 && program_pages != 0) {printf("\n             内存表");huanhang(memory_blocks);printf("|  块号  |");for (int i = 0; i < memory_blocks; i++) {printf("%3d |", i);}huanhang(memory_blocks);printf("|  页号  |");for (int i = 0; i < memory_blocks; i++) {printf("%3d |", memory_allocation[i]);}huanhang(memory_blocks);printf("\n             页表");huanhang(program_pages);printf("|  页号  |");for (int i = 0; i < program_pages; i++) {printf("%3d |",i);}huanhang(program_pages);printf("|物理块号|");for (int i = 0; i < program_pages; i++) {printf("%3d |", page_list[i].block_num);}huanhang(program_pages);printf("| 状态位 |");for (int i = 0; i < program_pages; i++) {if(page_list[i].state==true)printf("  y |");elseprintf("  n |");}huanhang(program_pages);printf("| 修改位 |");for (int i = 0; i < program_pages; i++) {if (page_list[i].modify == true)printf("  y |");elseprintf("  n |");}huanhang(program_pages);printf("|装载时间|");for (int i = 0; i < program_pages; i++) {printf("%3d |", page_list[i].visit.load_time);}huanhang(program_pages);printf("|频率顺序|");for (int i = 0; i < program_pages; i++) {printf("%3d |", page_list[i].visit.frequency);}huanhang(program_pages);}else {printf("\n尚未初始化，请先初始化数据\n");}}void simulation(int l,int f) {//模拟操作init(memory_blocks, program_pages);int lose = 0;int longth[PAGE_USE_LONGTH];for (int i = 0; i < l; i++) {int a;a=create_rand(0,program_pages-1);longth[i] = a;bool flag;flag = allocation_once(a, f);if (flag == false) {lose += 1;allocation_once(a, f);}}float m;float Lose = lose;float L = l;m = Lose / L;printf("\n随机访问序列为(页号) ");for (int i = 0; i < l; i++) {printf("%3d",longth[i]);}printf("\n\n缺页率为%.2f%%\n",m*100);}void menu(){//菜单函数printf("\n                             页面置换模拟\n");printf("\n初始化(init) 显示页表信息(show) 页面置换算法(FIFO)或(LRU) \n清屏(clear)\n");char code[20];while (1) {printf("\n");scanf("%s", code);if (_stricmp(code, "init") == 0) {//初始化memory_blocks = 0;program_pages = 0;int a, b;printf("\n请输入进程的分页数(最大%d)  ", PROGRAM_PAGES);scanf("%d", &a);while (a > PROGRAM_PAGES||a<1) {printf("\n输入数值非法,请重新输入", PROGRAM_PAGES);scanf("%d", &a);}printf("\n请输入为该进程分配的物理块数(最大%d)  ", MEMORY_BLOCKS);scanf("%d", &b);while (b > MEMORY_BLOCKS||b<1) {printf("\n输入数值非法,请重新输入", MEMORY_BLOCKS);scanf("%d", &b);}init(b,a);}else if (_stricmp(code, "show") == 0) {//显示功能show_me();}else if (_stricmp(code, "FIFO") == 0) {//先进先出置换int l;printf("\n请输入页面走向长度  ");scanf("%d",&l);simulation(l,FIFO);}else if (_stricmp(code, "LRU") == 0) {//最久未用置换int l;printf("\n请输入页面走向长度  ");scanf("%d", &l);simulation(l, LRU);}else if (_stricmp(code, "clear") == 0) {//清屏system("cls");printf("\n                             页面置换模拟\n");printf("\n初始化(init) 显示页表信息(show) 页面置换算法(FIFO)或(LRU) \n清屏(clear)\n");}else printf("命令无效，请重新输入\n");}}int main(){srand(time(NULL));menu();getchar();    return 0;}