Queue Concept and FIFO Principle in DSA C - Build from Scratch

Queue Concept and FIFO Principle

📖 Scenario: Imagine a ticket counter where people stand in a line. The first person to arrive is the first to get the ticket and leave. This is called FIFO - First In, First Out. We will create a simple queue to simulate this line.

🎯 Goal: Build a queue using an array in C that follows the FIFO principle. You will add people to the queue and remove them in the order they arrived.

📋 What You'll Learn

Create an integer array called queue with size 5

Create two integer variables front and rear to track the queue ends

Write a function enqueue to add an element to the queue

Write a function dequeue to remove an element from the queue

Print the queue elements after enqueue and dequeue operations

💡 Why This Matters

🌍 Real World

Queues are used in real life for lines at stores, printers, and task scheduling where order matters.

💼 Career

Understanding queues helps in software development for managing tasks, requests, and resources efficiently.

1

Create the queue array and initialize pointers

Create an integer array called queue with size 5. Also create two integer variables called front and rear. Initialize front to -1 and rear to -1.

DSA C

int queue[5];
int front = -1;
int rear = -1;
// Your code here

Hint

Think of front and rear as markers for the start and end of the line.

2

Add the enqueue function to add elements

Write a function called enqueue that takes an integer value and adds it to the queue. Inside the function, first check if rear is 4 (queue full). If full, print "Queue is full". Otherwise, increase rear by 1 and add value to queue[rear]. If front is -1, set it to 0.

DSA C

void enqueue(int value) {
    // Your code here
}

Hint

Remember to check if the queue is full before adding.

3

Add the dequeue function to remove elements

Write a function called dequeue that removes and returns the front element from the queue. If front is -1 or greater than rear, print "Queue is empty" and return -1. Otherwise, store queue[front] in a variable, increase front by 1, and return the stored value.

DSA C

int dequeue() {
    // Your code here
}

Hint

Check if the queue is empty before removing an element.

4

Test the queue by enqueueing and dequeueing

In the main function, enqueue the values 10, 20, and 30 using enqueue. Then dequeue one value and print it with printf. Finally, print the remaining queue elements from front to rear using a for loop.

DSA C

int main() {
    // Your code here
    return 0;
}

Hint

Use a loop from front to rear to print the queue elements.