Stack using link list in C

1: #include <stdio.h>
2: #include <malloc.h>
3: #include <ctype.h>
4: 
5: //stack implementation using link list
6: typedef struct node
7: {
8:   int data;
9:   struct node *next;
11: }stackNode;
12: 
13: stackNode *head = NULL;
14: int size = 0;
15: 

16: int push(stackNode **head, int data)
17: {
18:   stackNode *newNode = (stackNode*)malloc(sizeof(stackNode));
19:   if(newNode == NULL)
20:     return 0;
21:   
22:   newNode->data = data;
23:   newNode->next = NULL;
24:   
25:   if(*head == NULL)
26:   {
27:     *head = newNode;
28:     size++;
29:     return 1;
30:   }  
31:   else
32:   {
33:     newNode->next = *head;
34:     *head = newNode;
35:     size++;
36:     return 1;
37:   }
38: }
39: 
40: stackNode* pop(stackNode **head)
41: {
42:   stackNode *topNode = NULL;
43: 
44:   if(*head == NULL)
45:     return NULL;
46:   
47:   //top node is returned
48:   topNode = (stackNode*)malloc(sizeof(stackNode));
49:   if(topNode == NULL)
50:     return NULL;
51:     
52:   topNode->data = (*head)->data;
53:   topNode->next = NULL;
54:   
55:   stackNode *tempNode = *head;
57:   *head = (*head)->next;
58:   
59:   free(tempNode);
60:   tempNode = NULL;
62:   size--;
63:   
64:   return topNode;
65: }
66: 
67: int main(int argc, char **argv)
68: {
69:   int i = 0;
70:   stackNode* top;
71:   int topData = 0;
72:   for(;i < 2 ; i++)
73:     push(&head,i);
74:   
75:   printf("size of stack is %d \n", size);
77:   do
78:   {
79:     top =  pop(&head);
80:     if(top)
81:     {
82:       printf("poping the top %d \n",top->data);
83:       free(top);
84:       top = NULL;
85:     }
86:     else
87:     {  
88:       printf("stack empty \n");
89:     }
90:   }while(size);
91:   
92:   printf("size of stack is %d \n", size);
94:   getchar();
96:   return 0;
97: }
98: