paging.c

#include<stdio.h>
#include<stdlib.h>
int pgsize, memsize;
int nframes, nfree;
int frames[100];
typedef struct pagetable {
	int pageno;
	int frameno;
	struct pagetable* next;
}Pagetable;
Pagetable* process[10];
typedef struct freeframe {
	int frameno;
	struct freeframe* next;
}Freeframe;
Freeframe* fhead;
void printtable(Pagetable *head)
{
  for(Pagetable *temp = head; temp != NULL; temp = temp->next)
    printf("Page %d: Frame %d\n", temp->pageno, temp->frameno);
}
void allocate()
{
	int p, m, np;
	Pagetable *head, *temp, *prev;
	printf("Process ID: ");
	scanf("%d", &p);
	printf("Memory required in KB: ");
	scanf("%d", &m);
	np = m / pgsize;
	if(m*1.0/pgsize > np) np++; 
	printf("No. of pages = %d\n", np);
	if(np > nfree) {
		printf("Not available!\n");
		return;
	}
	for(int i = 0; i < np; i++)
	{
		temp = (Pagetable*)malloc(sizeof(Pagetable));		
		temp->pageno = i;
		temp->frameno = fhead->frameno;
		temp->next = NULL;
		Freeframe* t = fhead;
		fhead = fhead->next;
		free(t);
		nfree--;
		if(i == 0) head = temp;
		else prev->next = temp;
		prev = temp;
	}
	process[p] = head;
	printtable(process[p]);
}
void deallocate()
{
	int p;
	printf("PID: ");
	scanf("%d", &p);
	Pagetable *pd, *t, *d;
	int f;
	Freeframe *pf, *tf;
    pf = fhead;
	if(fhead != NULL) for(; pf->next != NULL; pf = pf->next);
	pd = process[p];
	if(process[p] == NULL) {
		printf("Not allocated!\n");
		return;
	}
	for(t = pd; t != NULL;)
	{
		d = t;
		f = d->frameno;
		tf = (Freeframe*)malloc(sizeof(Freeframe));
		tf->frameno = f;
		tf->next = NULL;
        if(pf != NULL) {
            pf->next = tf;
            pf = tf;
        }
        else {
            pf = tf;
            fhead = pf;
        }
		t = t->next;
        nfree++;
		free(d);
	}
	process[p] = NULL;
	printf("Deallocated!\n");
}
void showtables()
{
	for(int i = 0; i < 10; i++) {
        if(process[i] != NULL) printf("PID: %d\n", i);
        printtable(process[i]);
		if(process[i] != NULL) printf("\n");
	}
}
void addressmap()
{
	int p, la, pn, fn, o, pa;
	printf("PID: ");
	scanf("%d", &p);
	printf("Logical address: ");
	scanf("%d", &la);
	pn = la / (pgsize * 1024);
	o = la % (pgsize * 1024);
	Pagetable *h = process[p], *t;
	t = h;
	for(int i = 0; i < pn; i++)
	{
		t = t->next;
	}
	fn = t->frameno;
	pa = fn * pgsize * 1024 + o;
	printf("Physical address: %d\n", pa);
}
void showfree()
{
  for(Freeframe *temp = fhead; temp != NULL; temp = temp->next)
    printf("%d ", temp->frameno);
  printf("\n");
}
int main()
{
	Freeframe *temp, *prev;	
	printf("Total physical memory in KB: ");
	scanf("%d", &memsize);
	printf("Page size in KB: ");
	scanf("%d", &pgsize);
	nframes = memsize / pgsize;
	printf("No. of frames = %d\n", nframes);
	for(int i = 0; i < nframes/2; i++) {
		int fr = random()%nframes;		
        if(frames[fr] != 1) {
            frames[fr] = 1;
            nfree++;
            temp = (Freeframe*)malloc(sizeof(Freeframe));
            temp->frameno = fr;
            temp->next = NULL;
            if(nfree == 1) fhead = temp;
            else prev->next = temp;
            prev = temp;
        }
        else i--;
	}
	int ch = 0;
	do {
		printf("1. Process Request 2. Deallocate 3. Show all Page Tables 4. Show all Free Frames 5. Address Mapping 6. Exit\nChoice: ");
		scanf("%d", &ch);
		switch(ch) {
			case 1: allocate(); break;
			case 2: deallocate(); break;
			case 3: showtables(); break;
			case 4: showfree(); break;
			case 5: addressmap(); break;
			case 6: exit(0);
		}
	}while(1);
	return 0;
}