diff --git a/week3/Makefile b/week3/Makefile
new file mode 100644
index 0000000..39f1b26
--- /dev/null
+++ b/week3/Makefile
@@ -0,0 +1,2 @@
+stack:stack.c stack.h
+	gcc stack.c stack.h -Wall -o stack
diff --git a/week3/stack.c b/week3/stack.c
new file mode 100644
index 0000000..325614f
--- /dev/null
+++ b/week3/stack.c
@@ -0,0 +1,103 @@
+#include <stdio.h>
+#include <stdbool.h>
+#include <stdlib.h>
+
+#include <assert.h>
+
+#include "stack.h"
+
+int main() {
+	Stack stack;
+	double val;
+	CreateStack(&stack, 5);
+	Push(&stack, 5.0);
+	Push(&stack, 6.5);
+	Push(&stack, -3.0);
+	Push(&stack, -8.0);
+	DisplayStack(&stack);
+	if (Top(&stack, &val)) {
+		printf("Top: %f\n", val);
+	}
+	Pop(&stack, &val);
+	if (Top(&stack, &val)) {
+		printf("Top: %f\n", val);
+	}
+	while(!IsEmpty(&stack)) {
+		Pop(&stack, &val);
+	}
+	DisplayStack(&stack);
+	DestroyStack(&stack);
+	return 0;
+}
+
+bool CreateStack(Stack *stack, int size) {
+	assert(size > 0);
+
+	stack->data = (double *)malloc(sizeof(double) * size);
+	if (stack->data == NULL) {
+		return false;
+	}
+
+	stack->top = -1;
+	stack->size = size;
+
+	return true;
+}
+
+bool IsEmpty(Stack *stack) {
+	return stack->top < 0;
+}
+
+bool IsFull(Stack *stack) {
+	return stack->top >= stack->size;
+}
+
+bool Top(Stack *stack, double *x) {
+	if (IsEmpty(stack)) {
+		return false;
+	}
+	*x = stack->data[stack->top];
+	return true;
+}
+
+bool Push(Stack *stack, double x) {
+	if (IsFull(stack)) {
+		return false;
+	}
+	stack->data[++stack->top] = x;
+	return true;
+}
+
+bool Pop(Stack *stack, double *x) {
+	if (IsEmpty(stack)) {
+		return false;
+	}
+	*x = stack->data[stack->top--];
+	return true;
+}
+
+void DisplayStack(Stack *stack) {
+	double *top_p = stack->data + stack->top;
+
+	printf("top --> ");
+	
+	for (; top_p >= stack->data; top_p--) {
+
+		/* print top --> hint */
+		if (top_p != stack->data + stack->top) {
+			printf("        ");
+		}
+
+		printf("|  % .7f  |\n", *top_p);
+	}
+
+	/* print top --> hint */
+	if (top_p != stack->data + stack->top) {
+		printf("        ");
+	}
+
+	printf("+--------------+\n");
+}
+
+void DestroyStack(Stack *stack) {
+}
diff --git a/week3/stack.h b/week3/stack.h
new file mode 100644
index 0000000..2f8bf9f
--- /dev/null
+++ b/week3/stack.h
@@ -0,0 +1,23 @@
+#include <stdbool.h>
+
+typedef struct Stack_str {
+	int size;
+	int top;
+	double *data;
+} Stack;
+
+bool CreateStack(Stack *stack, int size);
+
+bool IsEmpty(Stack *stack);
+
+bool IsFull(Stack *stack);
+
+bool Top(Stack *stack, double *x);
+
+bool Push(Stack *stack, double x);
+
+bool Pop(Stack *stack, double *x);
+
+void DisplayStack(Stack *stack);
+
+void DestroyStack(Stack *stack);