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

#define MAX_SIZE 100

typedef struct
{
    int block_index;
} IndexBlock;

int disk[MAX_SIZE];
int disk_size = MAX_SIZE;
IndexBlock index_table[MAX_SIZE];
int free_list[MAX_SIZE];
int free_list_size = MAX_SIZE;

void initializeDisk()
{
    int i;
    for (i = 0; i < disk_size; i++)
    {
        disk[i] = -1;                    // -1 indicates free space
        index_table[i].block_index = -1; // -1 indicates unallocated block
        free_list[i] = i;                // Initialize free list
    }
}

int allocateIndexed(int num_blocks)
{
    if (free_list_size < num_blocks)
    {
        printf("Error: Not enough free space.\n");
        return -1;
    }

    int index_block_index = free_list[--free_list_size];
    index_table[index_block_index].block_index = free_list[--free_list_size]; // Allocate index block
    int i;
    for (i = 0; i < num_blocks; i++)
    {
        int data_block_index = free_list[--free_list_size];
        disk[index_table[index_block_index].block_index + i] = data_block_index; // Allocate data block
    }
    return index_block_index;
}

void freeIndexed(int index_block_index, int num_blocks)
{
    int i;
    for (i = 0; i < num_blocks; i++)
    {
        int data_block_index = disk[index_table[index_block_index].block_index + i];
        disk[data_block_index] = -1;                    // Mark data block as free
        free_list[free_list_size++] = data_block_index; // Add to free list
    }
    free_list[free_list_size++] = index_table[index_block_index].block_index; // Free index block
    index_table[index_block_index].block_index = -1;                          // Mark index block as unallocated
}

void displayDisk()
{
    int i;
    printf("Disk Status:\n");
    for (i = 0; i < disk_size; i++)
    {
        printf("%d ", disk[i]);
    }
    printf("\n");
}

int main()
{
    initializeDisk();

    int allocated_index_block = allocateIndexed(5);
    if (allocated_index_block != -1)
    {
        printf("Indexed allocation successful. Allocated index block at index %d.\n", allocated_index_block);
    }
    displayDisk();

    // Free the allocated space
    freeIndexed(allocated_index_block, 5);
    printf("Freed the allocated index block.\n");
    displayDisk();

    return 0;
}
by

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About C

C language is one of the most popular general-purpose programming language developed by Dennis Ritchie at Bell laboratories for UNIX operating system. The initial release of C Language was in the year 1972. Most of the desktop operating systems are written in C Language.

Key features:

  • Structured Programming
  • Popular system programming language
  • UNIX, MySQL and Oracle are completely written in C.
  • Supports variety of platforms
  • Efficient and also handle low-level activities.
  • As fast as assembly language and hence used as system development language.

Syntax help

Loops

1. If-Else:

When ever you want to perform a set of operations based on a condition if-else is used.

if(conditional-expression) {
   // code
} else {
   // code
}

You can also use if-else for nested Ifs and if-else-if ladder when multiple conditions are to be performed on a single variable.

2. Switch:

Switch is an alternative to if-else-if ladder.

switch(conditional-expression) {    
case value1:    
 // code    
 break;  // optional  
case value2:    
 // code    
 break;  // optional  
...    
    
default:     
 // code to be executed when all the above cases are not matched;    
}

3. For:

For loop is used to iterate a set of statements based on a condition.

for(Initialization; Condition; Increment/decrement){  
  // code  
}

4. While:

While is also used to iterate a set of statements based on a condition. Usually while is preferred when number of iterations are not known in advance.

while(condition) {  
 // code 
}

5. Do-While:

Do-while is also used to iterate a set of statements based on a condition. It is mostly used when you need to execute the statements atleast once.

do {
  // code 
} while (condition);

Arrays

Array is a collection of similar data which is stored in continuous memory addresses. Array values can be fetched using index. Index starts from 0 to size-1.

Syntax

One dimentional Array:

data-type array-name[size];

Two dimensional array:

data-type array-name[size][size];

Functions

Function is a sub-routine which contains set of statements. Usually functions are written when multiple calls are required to same set of statements which increases re-usuability and modularity.

Two types of functions are present in C

  1. Library Functions:

Library functions are the in-built functions which are declared in header files like printf(),scanf(),puts(),gets() etc.,

  1. User defined functions:

User defined functions are the ones which are written by the programmer based on the requirement.

How to declare a Function

return_type function_name(parameters);

How to call a Function

function_name (parameters)

How to define a Function

return_type function_name(parameters) {  
  //code
}