The document discusses different types of memory allocation in C programming. It describes implicit and explicit type casting, and the functions used for dynamic memory allocation - malloc(), calloc(), realloc(), and free(). Examples are provided to demonstrate how to allocate and reallocate memory at runtime using these functions. malloc() allocates a single block of memory, calloc() allocates multiple blocks, realloc() changes the size of previously allocated memory, and free() releases the allocated memory.

1. DMA
BY MOHAMMED TSJUDDIN

2. C PROGRAMMING
Type casting :
There are two types of type casting.
1)Inmlicit type casting
2)Explicit type casting
Implicit type casting : it is done by compiler
#include<stdio.h>
int main(){
int x = 10; // integer x
char y = 'a'; // character c
// y implicitly converted to int. ASCII
// value of 'a' is 97
x = x + y;
// x is implicitly converted to float
float z = x + 1.0;
printf("x = %d, z = %f", x, z);
return 0;

3. C PROGRAMMING
Explicit typecasting :
it have to develop by user.
#include<stdio.h>
int main(){
double x = 1.2;
// Explicit conversion from double to int
int sum = (int)x + 1;
printf("sum = %d", sum);
return 0;
}

4. C PROGRAMMING
Dynamic memory allocation :
The concept of dynamic memory allocation in c language enables the C
programmer to allocate memory at runtime. Dynamic memory
allocation in c language is possible by 4 functions of stdlib.h header file.
1)malloc()
2)calloc()
3)realloc()
4)free()

5. C PROGRAMMING
malloc() allocates single block of requested memory.
calloc() allocates multiple block of requested memory.
realloc() reallocates the memory occupied by malloc() or calloc()
functions.
free() frees the dynamically allocated memory.

6. C PROGRAMMING
#include <stdio.h>
#include <stdlib.h>
int main() {
// This pointer will hold the
// base address of the block created
int* ptr;
int n, i;
// Get the number of elements for the array
printf("Enter number of elements:");
scanf("%d",&n);
printf("Entered number of elements: %dn", n);
// Dynamically allocate memory using malloc()
ptr = (int*)malloc(n * sizeof(int));

7. C PROGRAMMING
// Check if the memory has been successfully
// allocated by malloc or not
if (ptr == NULL) {
printf("Memory not allocated.n");
exit(0);}
else {
// Memory has been successfully allocated
printf("Memory successfully allocated using malloc.n");
// Get the elements of the array
for (i = 0; i < n; ++i) {
ptr[i] = i + 1;}
// Print the elements of the array
printf("The elements of the array are: ");
for (i = 0; i < n; ++i) {
printf("%d, ", ptr[i]); }}
return 0; }

8. C PROGRAMMING
Calloc() Example:
#include <stdio.h>
#include <stdlib.h>
int main(){
// This pointer will hold the
// base address of the block created
int* ptr;
int n, i;
// Get the number of elements for the array
n = 5;
printf("Enter number of elements: %dn", n);
// Dynamically allocate memory using calloc()
ptr = (int*)calloc(n, sizeof(int));

9. C PROGRAMMING
// Check if the memory has been successfully
// allocated by calloc or not
if (ptr == NULL) {
printf("Memory not allocated.n");
exit(0);}
else {
// Memory has been successfully allocated
printf("Memory successfully allocated using calloc.n");
// Get the elements of the array
for (i = 0; i < n; ++i) {
ptr[i] = i + 1;}
// Print the elements of the array
printf("The elements of the array are: ");
for (i = 0; i < n; ++i) {
printf("%d, ", ptr[i]);}}
return 0;}

10. C PROGRAMMING
Example : Realloc
#include <stdio.h>
#include <stdlib.h>
int main(){
// This pointer will hold the
// base address of the block created
int* ptr;
int n, i;
// Get the number of elements for the array
n = 5;
printf("Enter number of elements: %dn", n);
// Dynamically allocate memory using calloc()
ptr = (int*)calloc(n, sizeof(int));

11. // Check if the memory has been successfully
// allocated by malloc or not
if (ptr == NULL) {
printf("Memory not allocated.n");
exit(0);}
else {
// Memory has been successfully allocated
printf("Memory successfully allocated using calloc.n");
// Get the elements of the array
for (i = 0; i < n; ++i) {
ptr[i] = i + 1;}
// Print the elements of the array
printf("The elements of the array are: ");
for (i = 0; i < n; ++i) {
printf("%d, ", ptr[i]);}

12. C PROGRAMMING
// Get the new size for the array
n = 10;
printf("nnEnter the new size of the array: %dn", n);
// Dynamically re-allocate memory using realloc()
ptr = realloc(ptr, n * sizeof(int));
// Memory has been successfully allocated
printf("Memory successfully re-allocated using realloc.n");
// Get the new elements of the array
for (i = 5; i < n; ++i) {
ptr[i] = i + 1;
}

13. C PROGRAMMING
// Print the elements of the array
printf("The elements of the array are: ");
for (i = 0; i < n; ++i) {
printf("%d, ", ptr[i]);
}
free(ptr);
}
return 0;
}