Write a C Program to implement Sequential File Allocation method.

Write a C Program to implement Sequential File Allocation method.

Description to Sequential File Allocation method: Files are normally stored on the disks. So the main problem is how to allocate space to those files. So that disk space is utilized effectively and files can be accessed quickly. Three major strategies of allocating disc space are in wide use. Sequential, indexed and linked.

Sequential allocation:

In this allocation strategy, each file occupies a set of contiguously blocks on the disk. This strategy is best suited. For sequential files, the file allocation table consists of a single entry for each file. It shows the filenames, starting block of the file and size of the file. The main problem with this strategy is, it is difficult to find the contiguous free blocks in the disk and some free blocks could happen between two files.

Algorithm for Sequential File Allocation:

Step 1: Start the program.

Step 2: Get the number of memory partition and their sizes.

Step 3: Get the number of processes and values of block size for each process.

Step 4: First fit algorithm searches all the entire memory block until a hole which is big enough is encountered. It allocates that memory block for the requesting process.

Step 5: Best-fit algorithm searches the memory blocks for the smallest hole which can be allocated to requesting process and allocates it.

Step 6: Worst fit algorithm searches the memory blocks for the largest hole and allocates it to the process.

Step 7: Analyses all the three memory management techniques and display the best algorithm which utilizes the memory resources effectively and efficiently.

Step 8: Stop the program.

/* Program to simulate sequential file allocation strategy */

Program Code:

#include < stdio.h>

#include<conio.h>

void main()

{

int f[50], i, st, len, j, c, k, count = 0;

clrscr();

for(i=0;i<50;i++)

f[i]=0;

printf("Files Allocated are : \n");

x: count=0;

printf(“Enter starting block and length of files: ”);

scanf("%d%d", &st,&len);

for(k=st;k<(st+len);k++)

if(f[k]==0)

count++;

if(len==count)

{

for(j=st;j<(st+len);j++)

if(f[j]==0)

{

f[j]=1;

printf("%d\t%d\n",j,f[j]);

}

if(j!=(st+len-1))

printf(” The file is allocated to disk\n");

}

else

printf(” The file is not allocated \n");

printf("Do you want to enter more file(Yes - 1/No - 0)");

scanf("%d", &c);

if(c==1)

goto x;

else

exit();

getch();

}

Program Output:

Files Allocated are :

Enter starting block and length of files: 14 3

14 1

15 1

16 1

The file is allocated to disk

Do you want to enter more file(Yes - 1/No - 0)1

Enter starting block and length of files: 14 1

The file is not allocated

Do you want to enter more file(Yes - 1/No - 0)1

Enter starting block and length of files: 14 4

The file is not allocated

Do you want to enter more file(Yes - 1/No - 0)0