MVT (Multiprogramming Variable Task) in C Programming

#include< stdio.h>
#include< conio.h>
void main()
{
 int i,os_m,nPage,total,pg[25];
 clrscr();
 printf("\nEnter total memory size:");
 scanf("%d",&total);

 printf("\nEnter memory for OS:");
 scanf("%d",&os_m);

 printf("\nEnter no. of pages:");
 scanf("%d",&nPage);
 for(i=0;i< nPage;i++)
 {
  printf("Enter size of page[%d]:",i+1);
  scanf("%d",&pg[i]);
 }
 total=total-os_m;

 for(i=0;i< nPage;i++)
 {
  if(total>=pg[i])
  {
   printf("\n Allocate page %d",i+1);
   total=total-pg[i];
  }
  else
   printf("\n page %d is not allocated due to insufficient memory.",i+1);
 }
 printf("\n External Fragmentation is:%d",total);
 getch();
}

OUTPUT

Enter total memory size:1024

Enter memory for OS:256

Enter no. of pages:4
Enter size of page[1]:128
Enter size of page[2]:512
Enter size of page[3]:64
Enter size of page[4]:512

 Allocate page 1
 Allocate page 2
 Allocate page 3
 page 4 is not allocated due to insufficient memory.
 External Fragmentation is:64