链式栈实现：

#include <stdio.h>

struct node
{
	int val;
	struct node *next;
};

typedef struct  node Node;
Node *base, *top;


void init_stack()
{
	base = top = NULL;
}

void push_stack(Node *newnode)
{
	if(base == top)
	{
		base = newnode;
		top = (Node*) malloc(sizeof(Node));
		top->next = newnode;
	}
	newnode->next = top->next;
	top->next = newnode;

	printf("%d\n", newnode->val);        //入栈顺序
}

int  pop_stack()
{
	int temp;
	Node *tp = top;
	
	if(base == NULL)
		printf("stack is empty!\n");
	
	temp = top->next->val;
	top = top->next;
	free(tp);

	return temp;
}

void show()                    //用于检验出栈是否正确，不属于栈的实现
{
	Node *p = top->next;
	while(p != base)
	{
		printf("%d ", p->val);
		p = p->next;
	}
	printf("%d ", p->val);
	putchar(10);
}

int main()
{
	init_stack();
	
	int i = 0;
	Node *newnode;
	for(i = 0; i < 5; i++)
	{
		newnode = (Node*) malloc(sizeof(Node));
		if(newnode)
		{
			newnode->val = i;
			push_stack(newnode);
		}
	}

	show();        //入栈后，从栈顶到栈底的数据
	
	printf("%d\n", pop_stack());    //取一个数

	show();        //出栈一个数后，从栈顶到栈底的数据
	
	return 0;
}

顺序栈的实现：

#include <stdio.h>
#include <time.h>
#include <stdlib.h>

#define STACK_INIT_SIZE 100		//栈的初始化大小
#define STACK_INCREASE  20		//栈的扩容

struct stack
{
	int *base;	//栈存放的数据类型，根据需要选择
	int *top;
	int stacksize;  //栈的大小
};

typedef struct stack Stack;

void create_stack(Stack **s)        //创建一个空栈
{
  	*s = (Stack*) malloc(sizeof(Stack));
	if(!*s)
		puts("create stack failed");
}

void stack_init(Stack *s)        //初始化栈
{
	s->base = (int*) malloc(sizeof(int) * STACK_INIT_SIZE);
	if(!(s->base))
		return;
	
	s->top = s->base;
	s->stacksize = STACK_INIT_SIZE;
}

void push_stack(Stack *s, int a)        
{
	if(s->top - s->base >= s->stacksize)  //栈满扩容
	{
		s->base = (int*) realloc(s->base, (s->stacksize+STACK_INCREASE)*sizeof(int)); 
	}
	if(!(s->base))                //扩容失败
	{
		puts("realloc failed");
		return;
	}

	s->top = s->base + s->stacksize;  //栈顶指针重新定位至扩充后的内容
	s->stacksize += STACK_INCREASE;   //栈大小重新赋值

	*s->top = a;    //入栈
	s->top++;

//	printf("pop stack %d\n", a);
}

void pop_stack(Stack* s)        //出栈
{
	if(s->top == s->base)		//栈空
		return;

	s->top--;
//	printf("%d\n", *s->top);
}

int main()
{
	Stack *s;
	
	create_stack(&s);
	stack_init(s);
	push_stack(s, 5);
	pop_stack(s);
	
	return 0;
}