stacks in c

#include <stdio.h>

int MAXSIZE = 8;       
int stack[8];     
int top = -1;            

int isempty() {

   if(top == -1)
      return 1;
   else
      return 0;
}
   
int isfull() {

   if(top == MAXSIZE)
      return 1;
   else
      return 0;
}

int peek() {
   return stack[top];
}

int pop() {
   int data;
	
   if(!isempty()) {
      data = stack[top];
      top = top - 1;   
      return data;
   } else {
      printf("Could not retrieve data, Stack is empty.\n");
   }
}

int push(int data) {

   if(!isfull()) {
      top = top + 1;   
      stack[top] = data;
   } else {
      printf("Could not insert data, Stack is full.\n");
   }
}

int main() {
   // push items on to the stack 
   push(3);
   push(5);
   push(9);
   push(1);
   push(12);
   push(15);

   printf("Element at top of the stack: %d\n" ,peek());
   printf("Elements: \n");

   // print stack data 
   while(!isempty()) {
      int data = pop();
      printf("%d\n",data);
   }

   printf("Stack full: %s\n" , isfull()?"true":"false");
   printf("Stack empty: %s\n" , isempty()?"true":"false");
   
   return 0;
}

// C program for array implementation of stack 
#include <limits.h> 
#include <stdio.h> 
#include <stdlib.h> 
  
// A structure to represent a stack 
struct Stack { 
    int top; 
    unsigned capacity; 
    int* array; 
}; 
  
// function to create a stack of given capacity. It initializes size of 
// stack as 0 
struct Stack* createStack(unsigned capacity) 
{ 
    struct Stack* stack = (struct Stack*)malloc(sizeof(struct Stack)); 
    stack->capacity = capacity; 
    stack->top = -1; 
    stack->array = (int*)malloc(stack->capacity * sizeof(int)); 
    return stack; 
} 
  
// Stack is full when top is equal to the last index 
int isFull(struct Stack* stack) 
{ 
    return stack->top == stack->capacity - 1; 
} 
  
// Stack is empty when top is equal to -1 
int isEmpty(struct Stack* stack) 
{ 
    return stack->top == -1; 
} 
  
// Function to add an item to stack.  It increases top by 1 
void push(struct Stack* stack, int item) 
{ 
    if (isFull(stack)) 
        return; 
    stack->array[++stack->top] = item; 
    printf("%d pushed to stack\n", item); 
} 
  
// Function to remove an item from stack.  It decreases top by 1 
int pop(struct Stack* stack) 
{ 
    if (isEmpty(stack)) 
        return INT_MIN; 
    return stack->array[stack->top--]; 
} 
  
// Function to return the top from stack without removing it 
int peek(struct Stack* stack) 
{ 
    if (isEmpty(stack)) 
        return INT_MIN; 
    return stack->array[stack->top]; 
} 
  
// Driver program to test above functions 
int main() 
{ 
    struct Stack* stack = createStack(100); 
  
    push(stack, 10); 
    push(stack, 20); 
    push(stack, 30); 
  
    printf("%d popped from stack\n", pop(stack)); 
  
    return 0; 
} 

typedef struct Nodo{
   Elem val;
   struct Nodo *next;
} *Stack;
Stack Empty(){return NULL;}
bool IsEmpty(Stack a){return a==NULL;}
Elem Top(Stack a){return a->val;} 
Stack Pop(Stack l){return l->next;}
Stack Push(Elem x,Stack res){
    Stack nuevo=(Stack)malloc(sizeof(struct Nodo));
    nuevo->val=x;
    nuevo->next=res;
    return nuevo;
}