alloc in c code example

Example 1: allocate memory c

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

Example 2: how to dynamically allocate array size in c

// declare a pointer variable to point to allocated heap space
int    *p_array;
double *d_array;

// call malloc to allocate that appropriate number of bytes for the array

p_array = (int *)malloc(sizeof(int)*50);      // allocate 50 ints
d_array = (int *)malloc(sizeof(double)*100);  // allocate 100 doubles


// use [] notation to access array buckets 
// (THIS IS THE PREFERED WAY TO DO IT)
for(i=0; i < 50; i++) {
  p_array[i] = 0;
}

// you can use pointer arithmetic (but in general don't)
double *dptr = d_array;    // the value of d_array is equivalent to &(d_array[0])
for(i=0; i < 50; i++) {
  *dptr = 0;
  dptr++;
}

Example 3: what is the use of malloc in c

In C, the library function malloc is used to allocate a block of memory on the heap. The program accesses this block of memory via a pointer that malloc returns. When the memory is no longer needed, the pointer is passed to free which deallocates the memory so that it can be used for other purposes.