How I Implemented a Stack Without Using Any Library (And What I Learned From It)

When I first started programming in C and C++, one of the most fascinating concepts to me was the stack data structure. It’s simple, elegant, and incredibly powerful. You push data in, pop data out, and everything works in a Last In, First Out (LIFO) fashion. Almost like stacking plates at a restaurant: the last plate you put on the pile is the first one you take off.

Most of the time, when we want to use a stack, we just import a library. In C++, for example, we can just use #include <stack> and be done with it. Problem solved, right? Well, not exactly.

I remember a moment in college when my professor gave us a challenge: “Implement a stack from scratch, without using any built-in library. Just raw pointers, arrays, or linked lists. That’s it.” At first, I thought it would be easy. But then, as I started coding, I realized this task would teach me more than I expected.

In this article, I want to share my experience implementing a stack without any library, step by step. I’ll also explain the lessons I learned from doing it the hard way, and why I think every beginner should try this at least once.

Why Implement a Stack Without a Library?

Before I get into my personal journey, let me explain why this is even worth doing:

1. Deeper Understanding
   Libraries are great for productivity, but they also make us lazy. By building a stack manually, I really had to understand how it works internally—memory allocation, array resizing, pointer manipulation, and error handling.

2. Problem-Solving Skills
   Debugging my own implementation forced me to think about edge cases: what happens when the stack is empty and I try to pop? What if the stack is full and I try to push more data?

3. Performance Awareness
   Implementing a stack myself made me more aware of how costly certain operations are, and why some data structures are faster in certain scenarios.

4. Confidence Boost
   There’s something incredibly satisfying about saying, “I built this myself.”

My First Attempt: Stack Using Arrays

Like most beginners, I decided to use a simple array first. Arrays are straightforward and easy to visualize, so they felt like the perfect starting point.

Here’s a simplified version of what I built in C:

#include <stdio.h>
#define MAX 100

int stack[MAX];
int top = -1;

void push(int value) {
    if (top == MAX - 1) {
        printf("Stack Overflow!\n");
        return;
    }
    stack[++top] = value;
}

int pop() {
    if (top == -1) {
        printf("Stack Underflow!\n");
        return -1;
    }
    return stack[top--];
}

int peek() {
    if (top == -1) {
        printf("Stack is empty!\n");
        return -1;
    }
    return stack[top];
}

int isEmpty() {
    return top == -1;
}

When I ran this, it worked fine for small experiments. I could push values, pop them, and peek at the top element. It gave me a good idea of how a stack behaves.

But there were limitations. The array size was fixed at 100. What if I wanted a stack of 10,000 elements? Or what if I didn’t know the size ahead of time? That’s when I realized I needed something more flexible.

The Next Step: Stack Using Linked List

My professor encouraged us to move on from arrays and try implementing a stack with a linked list. This was trickier but also much more dynamic.

Here’s the essence of what I coded:

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

struct Node {
    int data;
    struct Node* next;
};

struct Node* top = NULL;

void push(int value) {
    struct Node* newNode = (struct Node*)malloc(sizeof(struct Node));
    newNode->data = value;
    newNode->next = top;
    top = newNode;
}

int pop() {
    if (top == NULL) {
        printf("Stack Underflow!\n");
        return -1;
    }
    int value = top->data;
    struct Node* temp = top;
    top = top->next;
    free(temp);
    return value;
}

int peek() {
    if (top == NULL) {
        printf("Stack is empty!\n");
        return -1;
    }
    return top->data;
}

This version was more robust. I could push as many elements as I wanted (limited only by memory), and I didn’t need to worry about predefined sizes.

But again, I ran into some challenges:

• I had to manage memory manually (malloc and free).

• Debugging was harder, especially when I accidentally messed up pointers.

• Forgetting to free memory caused leaks.

And honestly? I remember staying up late one night, pulling my hair out because my program kept crashing. After hours of debugging, I found the culprit: I was trying to pop from an empty stack without checking first. That bug taught me a valuable lesson: always handle edge cases.

What I Learned from the Experience

Looking back, here are the key takeaways from implementing stacks without libraries:

1. Error Handling Matters
   A stack overflow or underflow may sound funny in theory, but in practice, if you don’t check for them, your program will crash.

2. Pointers Are Tricky But Essential
   Working with linked lists forced me to get comfortable with pointers. At first, I hated them. Now, I see them as powerful tools when handled carefully.

3. Memory Management Can’t Be Ignored
   In languages like C and C++, you are responsible for freeing memory. Forgetting to do so causes leaks, and freeing memory incorrectly can corrupt your program.

4. Appreciation for Libraries
   After going through this pain, I now appreciate built-in libraries so much more. When I write std::stack<int> myStack; in C++, I know exactly what’s happening under the hood.

Why You Should Try This Too

If you’re new to programming, I highly recommend trying this exercise. Yes, it might feel frustrating. Yes, you’ll probably encounter segmentation faults. But the learning experience is worth it.

You’ll come out of it with:

• A solid grasp of how stacks really work.

• Stronger debugging skills.

• A sense of accomplishment that makes you proud.

And who knows? Maybe someday you’ll be building something bigger (like a custom memory allocator or even parts of an operating system), and you’ll realize these fundamental lessons were the foundation.

When I look back, implementing a stack without using libraries wasn’t just an academic exercise. It was a journey that helped me grow as a programmer.

I still remember the thrill of seeing my first push and pop operations work correctly. I also remember the frustration of debugging endless pointer errors. But most importantly, I remember the feeling of finally mastering the concept.

Today, whenever I use a built-in stack, I smile a little. Because I know what’s happening inside. And that knowledge gives me confidence that I can tackle even bigger programming challenges in the future.

So, if you’ve never tried implementing a stack from scratch give it a shot. Trust me, you’ll learn more than you expect.