diff --git a/stack.c b/stack.c
index b7177fb..e9b7646 100644
--- a/stack.c
+++ b/stack.c
@@ -1,23 +1,28 @@
 #include <stdio.h>
 #include <stdlib.h>
+#include <assert.h>
+#include <stdbool.h>
 
-typedef struct {
+#include "stack.h"
+
+struct Stack {
 	void** data;
 	int top_index;
 	int capacity;
 	int curr_size;
-} Stack;
+};
 
 Stack* new_stack(int stack_size) {
-	Stack* stack = malloc(sizeof(Stack));
-	stack->capacity = stack_size;
-	stack->data = malloc(stack_size);
-	stack->top_index = 0;
-	stack->curr_size = 0;
-	return stack;
+	assert(stack_size > 0);
+	Stack* my_stack = malloc(sizeof(Stack));
+	my_stack->capacity = stack_size;
+	my_stack->data = malloc(stack_size);
+	my_stack->top_index = 0;
+	my_stack->curr_size = 0;
+	return my_stack;
 }
 
-void push(Stack* stack,void* element) {
+void stack_push(Stack* stack,void* element) {
 	if (stack->curr_size >= stack->capacity-1) {
 		stack->data = realloc(stack->data, stack->capacity*2);
 		stack->capacity *= 2;
@@ -29,7 +34,8 @@ void push(Stack* stack,void* element) {
 	return;
 }
 
-void* pop(Stack* stack) {
+void* stack_pop(Stack* stack) {
+	assert( !(stack_isEmpty(stack)) );
 	stack->top_index--;
 	void* to_return = *(stack->data + stack->top_index);
 	*(stack->data + stack->top_index) = NULL;
@@ -39,25 +45,18 @@ void* pop(Stack* stack) {
 	return to_return;
 }
 
-void* peek(Stack* stack) {
+void* stack_peek(Stack* stack) {
 	void* to_return = *(stack->data + stack->top_index - 1);
 	return to_return;
 }
 
-int size(Stack* stack) {
+int stack_size(Stack* stack) {
 	return (stack->curr_size);
 }
 
-void main() {
-	Stack* stack = new_stack(10);
-	int a = 2;
-	int b = 3;
-	int c = 4;
-	push(stack,(void *)&a);
-	push(stack,(void *)&b);
-	push(stack,(void *)&c);
-	printf("%d\n",*( (int *) pop(stack)));
-	printf("%d\n",*( (int *) pop(stack)));
-	printf("%d\n",*( (int *) pop(stack)));
-//	printf("%d\n",size(stack));
+bool stack_isEmpty(Stack* stack) {
+	if (stack_size(stack) == 0) {
+		return true;
+	}
+	return false;
 }
diff --git a/stack.h b/stack.h
new file mode 100644
index 0000000..56ab7cf
--- /dev/null
+++ b/stack.h
@@ -0,0 +1,11 @@
+#include <stdbool.h>
+
+typedef struct Stack Stack;
+
+Stack* new_stack(int stack_size);
+
+void stack_push(Stack* stack, void* element);
+void* stack_pop(Stack* stack);
+void* stack_peek(Stack* stack);
+int stack_size(Stack* stack);
+bool stack_isEmpty(Stack* stack);