#include <stdlib.h>
  void *malloc( size_t size );

The function malloc() returns a pointer to a chunk of memory of size size, or NULL if there is an error. The memory pointed to will be on the heap, not the stack, so make sure to free it when you are done with it. An example:

   typedef struct data_type {
     int age;
     char name[20];
   } data;              

   data *bob;
   bob = (data*) malloc( sizeof(data) );
   if( bob != NULL ) {
     bob->age = 22;
     strcpy( bob->name, "Robert" );
     printf( "%s is %d years old\n", bob->name, bob->age );
   }
   free( bob );