用C语言写一个程序：1.Setup a simulating backing store in memory. Read the data from pdata.bin to this backing store. 2.Initialize a page table for process p, set the frame number to be -1 for each page, indicating that the page is not loaded into memory yet. 3.Read logical addresses one by one from la.txt. 4.For each logical address, a)if its page has been loaded into physical memory, simply find the frame number in the page table, then generate physical address, find and print out the physical address and data inside this address. b)if the page is used for the first time, i.e., in page table, its frame number is -1，then the page that contains this address should be loaded into a free frame in physical memory (RAM). Then update the page table by adding the frame number to the right index in the page table. Then repeat 4a). Assumption: 1.Assume the file la.txt includes the sequence of generated addresses from CPU. 2.Use a part of memory as backing store that store data for a process. 3.The backing store size is 128 bytes 4.The size of process p is 128 bytes. 5.The contents of p is included in a file pdata.bin which is a binary file. 6.Use a part of memory as RAM. The size of physical memory is 256 bytes, from 0 to 255. All the physical memory is available, allocating starting from beginning in sequence. That is, allocate frame 0 first, then frame 1, then frame 2…. 7.The size of a frame is 32 bytes, i.e., 5 bits for the offset in a frame, total number of frames is 8. At beginning, no page table is available for process p.

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

#define PAGE_SIZE 32
#define FRAME_SIZE 32
#define PAGE_TABLE_SIZE 4
#define BACKING_STORE_SIZE 128
#define RAM_SIZE 256

typedef struct {
    int frame_number;
} page_table_entry;

int main() {
    // Step 1: Setup a simulating backing store in memory. Read the data from pdata.bin to this backing store.
    FILE *pdata_file = fopen("pdata.bin", "rb");
    if (pdata_file == NULL) {
        printf("Error: failed to open pdata.bin\n");
        return 1;
    }
    char backing_store[BACKING_STORE_SIZE];
    fread(backing_store, sizeof(char), BACKING_STORE_SIZE, pdata_file);
    fclose(pdata_file);

    // Step 2: Initialize a page table for process p, set the frame number to be -1 for each page.
    page_table_entry page_table[PAGE_TABLE_SIZE];
    for (int i = 0; i < PAGE_TABLE_SIZE; i++) {
        page_table[i].frame_number = -1;
    }

    // Step 3: Read logical addresses one by one from la.txt.
    FILE *la_file = fopen("la.txt", "r");
    if (la_file == NULL) {
        printf("Error: failed to open la.txt\n");
        return 1;
    }
    int logical_address, page_number, offset, frame_number;
    char data;
    while (fscanf(la_file, "%d", &logical_address) == 1) {
        // Step 4a: if its page has been loaded into physical memory, simply find the frame number in the page table, then generate physical address, find and print out the physical address and data inside this address.
        page_number = logical_address / PAGE_SIZE;
        offset = logical_address % PAGE_SIZE;
        if (page_table[page_number].frame_number != -1) {
            frame_number = page_table[page_number].frame_number;
            int physical_address = frame_number * FRAME_SIZE + offset;
            data = backing_store[page_number * PAGE_SIZE + offset];
            printf("Logical address: %d, Physical address: %d, Data: %c\n", logical_address, physical_address, data);
        }
        // Step 4b: if the page is used for the first time, i.e., in page table, its frame number is -1，then the page that contains this address should be loaded into a free frame in physical memory (RAM). Then update the page table by adding the frame number to the right index in the page table. Then repeat 4a).
        else {
            for (int i = 0; i < RAM_SIZE / FRAME_SIZE; i++) {
                if (page_table[i].frame_number == -1) {
                    page_table[i].frame_number = i;
                    frame_number = i;
                    int physical_address = frame_number * FRAME_SIZE + offset;
                    for (int j = 0; j < FRAME_SIZE; j++) {
                        backing_store[page_number * PAGE_SIZE + j] = backing_store[page_number * PAGE_SIZE + j];
                    }
                    data = backing_store[page_number * PAGE_SIZE + offset];
                    printf("Logical address: %d, Physical address: %d, Data: %c\n", logical_address, physical_address, data);
                    break;
                }
            }
        }
    }
    fclose(la_file);

    return 0;
}