YourType *p;
p = (YourType *)calloc (no_of_elements, sizeof (YourType));
if (p==NULL) {
fprintf (stderr, "Out of memory\n");
exit (32);
}
malloc is a function of the standard c library (stdlib) and it is abbreviation for memory allocate. What this function does is allocates memory in the RAM of computer to store variable data in it. You will use it whenever you need a place to store you temporary data such as an array or structure. To use malloc all you have to do is call malloc and tell it the size of the memory you want. It will then return a pointer to that memory. persumabely if it fails it returns NULL.
You use a 2-D array with malloc the same way you use any other structure or scalar with malloc. The malloc library call takes a single argument of type size_t (in bytes) and returns a void* pointer to a region of memory that is suitably aligned for any supported data type. An example using the 2-D array... int *myArray[10][20]; myArray = malloc (sizeof (myArray)); if (myArray == NULL) {...exception processing...}; Note that a 2-D array is really the same as a 1-D array - its a linear region of memory - its just that the compiler does address arithmetic for you.
The malloc() function is part of a class of functions that deal with the allocation of memory on the heap. int *a = malloc (sizeof (int) * 100); /* allocate 100 int's */ if (a == NULL) {...} /* deal with possible malloc failure */ /* use a, either as pointer or as array of 100 ints */ free (a); /* release memory back to the library */
The malloc function is a function used in C/C++ and various other high-level programming languges to add memory to the heap, it is essentially a pointer int* X = malloc(sizeof(int)); Where the parameter to malloc is the number of bytes you want to make room for. Because we are using an integral variable we want to make as much room as an integer takes.
Its simple void main() { int *arr[10]; arr=(int*)malloc(sizeof(int)*10); ...... ...... ...... ...... free(arr); }
In C, malloc is used to reserve a predetermined size of memory. void * malloc ( size_t size ); calloc is used to reserve a chunk of memory large enough to store num elements, each of a predetermined size. void * calloc ( size_t num, size_t size ); To create a char array of size 10 you can do it in one of two ways: char* mChars = malloc( 10 * sizeof(char) ); char* cChars = calloc( 10, sizeof(char) ); There is no concept of malloc or calloc in Java.
#include <stdlib.h> int **array1 = malloc(nrows * sizeof(int *)); for(i = 0; i < nrows; i++) array1[i] = malloc(ncolumns * sizeof(int));
an array is a collection of the same data type.
Yes, arrays can be created dynamically. The following shows how it can be done in C: void f (unsigned n) { int* p = malloc (n * sizeof (int)); /* allocate memory to accommodate n integers */ /* use p... */ free (p); p = 0; }
To determine the size of an array in C using the keyword sizeof, you would use the syntax: sizeof(array) / sizeof(array0).
The array name is a reference to the start address of the array, so simply take its address. int a[10]; int* p1 = &a; If the array is allocated on the heap, then there is no name (all allocations on the heap are anonymous). However, you don't need a name since you already know the address: int* p2 = malloc (10 * sizeof (int));
There is no "NULL array" as such, you may take a pointer to an array and set it to NULL (binary 0) e.g. int* foo; // Declare a pointer foo = malloc( 40 * sizeof(int)); //Allocate an array of 40 integers pointed to by "foo" foo = NULL; //Set the pointer to NULL, if you're using a garbage collector this should trigger an automatic free() of the memory allocated to the array. If you are NOT using a garbage collector (which is more common in C) this line is a memory leak.