malloc in c

1// Use malloc to allocate memory
2ptr = (castType*) malloc(size);
3int *exampl = (int*) malloc(sizeof(int));
4// Use calloc to allocate and inizialize n contiguous blocks of memory
5ptr = (castType*) calloc(n, size);
6char *exampl = (char*) calloc(20, sizeof(char));

1/* malloc example: random string generator*/
2#include <stdio.h>      /* printf, scanf, NULL */
3#include <stdlib.h>     /* malloc, free, rand */
4
5int main ()
6{
7  int i,n;
8  char * buffer;
9
10  printf ("How long do you want the string? ");
11  scanf ("%d", &i);
12
13  buffer = (char*) malloc (i+1);
14  if (buffer==NULL) exit (1);
15
16  for (n=0; n<i; n++)
17    buffer[n]=rand()%26+'a';
18  buffer[i]='\0';
19
20  printf ("Random string: %s\n",buffer);
21  free (buffer);
22
23  return 0;
24}

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 main(int argc, char *argv[])
2{
3    int* memoireAllouee = NULL;
4
5    memoireAllouee = malloc(sizeof(int));
6    if (memoireAllouee == NULL) // Si l'allocation a échoué
7    {
8        exit(0); // On arrête immédiatement le programme
9    }
10
11    // On peut continuer le programme normalement sinon
12
13    return 0;
14}
15

1// Let's allocate enough space on the heap for an array storing 4 ints
2
3intArray = (int *) malloc(4 * sizeof(int)); // A pointer to an array of ints
4
5intArray[0] = 10;
6intArray[1] = 20;
7intArray[2] = 25;
8intArray[3] = 35;

1int main(int argc, char *argv[])
2{
3    int* string = NULL;
4
5    memoireAllouee = malloc(sizeof(int));
6    if (string == NULL) 
7    {
8    	return;
9   		string[0] = 'H';
10        string[1] = 'e';
11        string[2] = 'y';
12        string[3] = '!';
13        string[4] = '\0';
14        printf("%s\n", string);
15    }
16
17
18
19    return 0;