1	#include "stdio.h"
     2	
     3	#define MAX 5 // stack size 
     4	
     5	int push(int);
     6	void show_stack(void);
     7	void init_stack(void);
     8	int pop(void);
     9	
    10	int top=-1; // index , orignal empty
    11	int stack[MAX];
    12	
    13	int main(){
    14	
    15	 int i;
    16	 init_stack();
    17	
    18	 for (i=0; i < 7; i++){
    19	  push(i);
    20	 }
    21	
    22	 for (i=0; i<5; i++){
    23	  pop();
    24	 }
    25	 
    26	 show_stack();
    27	
    28	 return 0;
    29	} //end main
    30	
    31	// return 0 if succeed and 1 for fail
    32	// allow only positive number include 0
    33	
    34	int push(int data){
    35	 // FULL
    36	 if (top == MAX-1){
    37	  return 1;
    38	 }
    39	 else {
    40	  stack[++top]=data;   
    41	  return 0;
    42	 }
    43	} //end push
    44	
    45	// return 0 if ok
    46	int pop(){
    47	
    48	 int r;
    49	
    50	 if (top == -1){
    51	  return -1;
    52	 }
    53	 else {
    54	  r=stack[top];
    55	  stack[top]=-1;
    56	  top--;
    57	  return r;
    58	 }
    59	} //end pop
    60	
    61	void show_stack(){
    62	 int i;
    63	
    64	 for (i=0; i<MAX; i++){
    65	  printf("%d ", stack[i]);
    66	 }
    67	 printf("top=%d\n", top);
    68	} //end show_stack
    69	
    70	void init_stack(){
    71	 int i;
    72	
    73	 for (i=0; i<MAX; i++){
    74	  stack[i]=-1;
    75	 }
    76	} //end init_stack