#define MAXSTACK    10
typedef char StackEntry;
typedef enum boolean { FALSE, TRUE } Boolean;
typedef struct stack {
    int  top;
    StackEntry entry[MAXSTACK];
} Stack;

Boolean StackEmpty(Stack *s) {
  return s->top <= 0;
}

Boolean StackFull(Stack *s) {
    return s->top >= MAXSTACK;
}

void CreateStack(Stack *s) {
  s->top = 0;
}

void Push(StackEntry item, Stack *s) {
    if (StackFull(s)) { printf("Stack is full\n"); exit(0); }
    else s->entry[s->top++] = item;
}

void Pop(StackEntry *item, Stack *s) {
  if (StackEmpty(s)) { printf("Stack is empty"); exit(0); }
  else *item = s->entry[--s->top];
}

void main() {
  Stack s;
  int x;

  CreateStack(&s);
  Push('a', &s); Push('b', &s); Push('c', &s);

  while (!StackEmpty(&s)) {
    Pop(&x, &s);  printf("%c ",x);
  }
  printf("\n");
}