dynamic memory allocation in c

1#include <stdlib.h>
2
3void *malloc(size_t size);
4
5void exemple(void)
6{
7  char *string;
8  
9  string = malloc(sizeof(char) * 5);
10  if (string == NULL)
11    return;
12  string[0] = 'H';
13  string[1] = 'e';
14  string[2] = 'y';
15  string[3] = '!';
16  string[4] = '\0';
17  printf("%s\n", string);
18  free(string);
19}
20
21/// output : "Hey!"

1int *p = new int; // request memory
2*p = 5; // store value
3
4cout << *p << endl; // Output is 5
5
6delete p; // free up the memory
7
8cout << *p << endl; // Output is 0

1ptr = (castType*)calloc(n, size);

1char* pvalue  = NULL;         // Pointer initialized with null
2pvalue  = new char[20];       // Request memory for the variable
3

1#include <iostream>
2using namespace std;
3
4int main () {
5   double* pvalue  = NULL; // Pointer initialized with null
6   pvalue  = new double;   // Request memory for the variable
7 
8   *pvalue = 29494.99;     // Store value at allocated address
9   cout << "Value of pvalue : " << *pvalue << endl;
10
11   delete pvalue;         // free up the memory.
12
13   return 0;
14}

1C Dynamic Memory Allocation can be defined as a procedure in which the size of a data structure (like Array) is changed during the runtime.
2C provides some functions to achieve these tasks. There are 4 library functions provided by C defined under <stdlib.h> header file to facilitate dynamic memory allocation in C programming. They are: 
3 
4
5malloc()
6calloc()
7free()
8realloc()