#include <stdio.h>
#include <stdlib.h>
#define MAX_SIZE 100

typedef struct
{
    int start_block;
    int num_blocks;
} FileAllocation;

typedef struct node
{
    int block_index;
    struct node *next;
} BlockNode;

int disk[MAX_SIZE];
int disk_size = MAX_SIZE;
BlockNode *free_list = NULL;

void initializeDisk()
{
    int i;
    for (i = 0; i < disk_size; i++)
    {
        disk[i] = -1; // -1 indicates free space
    }
}

int allocateLinked(int num_blocks)
{
    if (free_list == NULL)
    {
        printf("Error: Disk is full.\n");
        return -1;
    }

    int start_block = free_list->block_index;
    BlockNode *current = free_list;
    int count = 0;
    while (current != NULL && count < num_blocks)
    {
        disk[current->block_index] = 1; // Mark block as allocated
        count++;
        current = current->next;
    }

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

    free_list = current; // Update free list
    return start_block;
}

void freeLinked(int start_block, int num_blocks)
{
    int i;
    for (i = start_block; i < start_block + num_blocks; i++)
    {
        disk[i] = -1; // Mark blocks as free
        BlockNode *new_node = (BlockNode *)malloc(sizeof(BlockNode));
        new_node->block_index = i;
        new_node->next = free_list;
        free_list = new_node; // Add to the beginning of free list
    }
}

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

int main()
{
    initializeDisk();

    // Simulate free blocks in disk
    BlockNode *temp = NULL;
    int i;
    for (i = 0; i < disk_size; i += 5)
    {
        BlockNode *new_node = (BlockNode *)malloc(sizeof(BlockNode));
        new_node->block_index = i;
        new_node->next = temp;
        temp = new_node;
    }
    free_list = temp;

    int allocated_block = allocateLinked(7);
    if (allocated_block != -1)
    {
        printf("Linked allocation successful. Allocated block starting at index %d.\n", allocated_block);
    }
    displayDisk();

    // Free the allocated space
    freeLinked(allocated_block, 7);
    printf("Freed the allocated block.\n");
    displayDisk();

    return 0;
}
by

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Read inputs from stdin

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#include <stdio.h>
int main()
{
    char name[50];
    printf("Enter name:");
    scanf("%s", name);
    printf("Hello %s \n" , name );
    return 0;
    
}

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
}