Objective: -In C translate a virtual address to a physical address, involving a
ID: 3717968 • Letter: O
Question
Objective:
-In C translate a virtual address to a physical address, involving a custom-sized fully associative page table.
Inputs:
-The total size of physical memory (in words)
-The page size (words/page)
-The replacement policy (LRU, FIFO)
Outputs:
-The corresponding physical address for a virtual address A message indicating a page fault (if any) in the page table
Specification:
-The program translates a virtual address to a physical address based on choosing from a menu of choices, where each choice calls the appropriate procedure, where the choices are:
a) Set parameters
b) Map virtual address
c) Quit program
-Upon entering the parameters, the page table is to be dynamically allocated based on the total number of page frames. The virtual pages will be mapped to the page frames on demand in the page frame order 0,1,2,3,…
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TEST RUN EXMPLE
Use below to test the program, yours should run exactly the same and have same outputs
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-------------------------------------------------------
Virtual memory to Main memory mapping:
-------------------------------------------------------
a) Enter parameters
b) Map virtual address
c) Quit
Enter selection: a
Enter main memory size (words): 2048
Enter page size (words/page): 1024
Enter replacement policy (0=LRU, 1=FIFO): 0
-------------------------------------------------------
Virtual memory to Main memory mapping:
-------------------------------------------------------
a) Enter parameters
b) Map virtual address
c) Quit
Enter selection: b
Enter virtual memory address to access: 5000
Page fault!
-----------------
| VP | PF |
-----------------
| 4 | 0 |
-----------------
-------------------------------------------------------
Virtual memory to Main memory mapping:
-------------------------------------------------------
a) Enter parameters
b) Map virtual address
c) Quit
Enter selection: b
Enter virtual memory address to access: 2048
Page fault!
-----------------
| VP | PF |
-----------------
| 4 | 0 |
-----------------
| 2 | 1 |
-----------------
-------------------------------------------------------
Virtual memory to Main memory mapping:
-------------------------------------------------------
a) Enter parameters
b) Map virtual address
c) Quit Enter selection:
b Enter virtual memory address to access: 4509
Virtual address 4509 maps to physical address 413
-----------------
| VP | PF |
-----------------
| 2 | 1 |
-----------------
| 4 | 0 |
-----------------
-------------------------------------------------------
Virtual memory to Main memory mapping:
-------------------------------------------------------
a) Enter parameters
b) Map virtual address
c) Quit Enter selection: b
Enter virtual memory address to access: 7160
Page fault!
-----------------
| VP | PF |
-----------------
| 4 | 0 |
-----------------
| 6 | 1 |
-----------------
-------------------------------------------------------
Virtual memory to Main memory mapping:
-------------------------------------------------------
a) Enter parameters
b) Map virtual address
c) Quit
Enter selection: c
Explanation / Answer
ANSWER:-
#include <stdio.h>
#include <stdlib.h>
//Parameters to enter
int sizeOfMainMemory;
int sizeOfPage;
int replacementPolicy;//Can be either 1 or 0
int numPages;
int choice;//user selection for options
struct pageTable {
//Page frames will be mapped to virtual pages
int pageFrame;
int virtualPage;
} *memory;
void enterParameters() {
printf("Enter main memory size (words):");
scanf("%d", &sizeOfMainMemory);
printf("Enter page size (words/page):");
scanf("%d", &sizeOfPage);
printf("Enter replacement policy (0=LRU, 1=FIFO): ");
scanf("%d", &replacementPolicy);
numPages = sizeOfMainMemory / sizeOfPage;
memory = (struct pageTable *)malloc(numPages * sizeof(struct pageTable));
int i;
for (i = 0; i < numPages; i++) {
//Flag each member of struct's index as -1
memory[i].pageFrame = -1;
memory[i].virtualPage = -1;
}
}
void mapVA() {
int VMAddress;//From user
int realAddress;//Generated
int virtualPage;
int offset;
printf("Enter virtual memory address to access: ");
scanf("%d", &VMAddress);
//Calculate offset and virtual page
offset = VMAddress % sizeOfPage;
virtualPage = VMAddress / sizeOfPage;
int i;
for (i = 0; i < numPages; i++) {
//if there is a hit (page in memory)
if (memory[i].virtualPage == virtualPage) {
realAddress = (memory[i].pageFrame * sizeOfPage) + offset;
//LRU
if (replacementPolicy == 0) {
int pfHolder;//placeholder for pageframe
int vpHolder;//placeholder for virtualpage
int g;
for (g = i; g < numPages - 1; g++) {
//Shift page table at index of hit
pfHolder = memory[g].pageFrame;
vpHolder = memory[g].virtualPage;
memory[g] = memory[g + 1];
memory[g + 1].pageFrame = pfHolder;
memory[g + 1].virtualPage = vpHolder;
}
}
printf("Virtual Address: %d maps to physical address %d", VMAddress,realAddress);
i = numPages-1;
}
//if theres a blank space
else if (memory[i].virtualPage == -1) {
//map virtual page to generated virtual page
memory[i].virtualPage = virtualPage;
//map pageframe to current index
memory[i].pageFrame = i;
printf("Page fault! ");
//set index to last element
i = numPages - 1;
}
else if (i == numPages - 1) {//condition for last element
memory[0].virtualPage = virtualPage;
int pfHolder;//placeholder for pageframe
int vpHolder;//placeholder for virtualpage
int h;
for (h = 0; h < numPages - 1; h++) {
//shift page table from beginning
pfHolder = memory[h].pageFrame;
vpHolder = memory[h].virtualPage;
memory[h] = memory[h + 1];
memory[h + 1].pageFrame = pfHolder;
memory[h + 1].virtualPage = vpHolder;
}
printf("Page Fault! ");
}
}
printf(" ---------------------- ");
printf("| VP | PF | ");
printf("---------------------- ");
for (i = 0; i < numPages; i++) {
if (memory[i].pageFrame != -1 && memory[i].virtualPage != -1) {//To avoid unnecessary printing
printf("| %d |", memory[i].virtualPage);
printf(" %d |", memory[i].pageFrame);
printf(" ---------------------- ");
}
}
}
int main() {
int boolean = 0;
while (!boolean) {
printf("Virtual memory to Main memory mapping: ");
printf("------------------------------------ ");
printf("1) Enter parameters ");
printf("2) Map virtual address ");
printf("3) Quit: ");
scanf("%d", &choice);
if (choice == 1) {
enterParameters();
}
else if (choice == 2) {
mapVA();
}
else if (choice == 3) {
return 0;
}
else//Catches anything outside of 1-3
printf("Invalid Entry");
printf(" ");
printf(" ");
}
}
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