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🎲 Unit 5: Arrays Made Simple

Welcome back, eager learner! 👋
Today we’re exploring Arrays — a magical way of keeping lots of values in one tidy place.
Instead of juggling variables everywhere, arrays let you line them up neatly like books on a shelf. 📚

🌟 Why Use Arrays?​

Imagine This

Without arrays, managing 100 student marks means writing 100 separate variables. 😵
With arrays, you just say: “Hey, here’s one variable that can hold 100 values!”

int student1 = 85;
int student2 = 90;
int student3 = 78;
int student4 = 92;
int student5 = 88;
// Imagine managing 100 students!

🔑 Key Characteristics​

PropertyDescription
Fixed SizeDecide size at declaration
Same Data TypeAll elements must be of same type
Contiguous MemoryStored side by side in memory
Zero-IndexedFirst element is at index 0
Random AccessAccess any element directly

🎯 One-Dimensional Arrays​

📜 Declaration Syntax​

datatype array_name[size];

// Examples
int numbers[10];      // Array of 10 integers
float prices[50];     // Array of 50 floats
char name[30];        // Array of 30 characters (string)

🌱 Initialization Styles​

int marks[5] = {85, 90, 78, 92, 88};

🧠 Memory Representation​

Array: int arr[5] = {10, 20, 30, 40, 50};

Memory:
Address:  1000   1004   1008   1012   1016
        ┌──────┬──────┬──────┬──────┬──────┐
Value:  │  10  │  20  │  30  │  40  │  50  │
        └──────┴──────┴──────┴──────┴──────┘
Index:     0      1      2      3      4

🛠 Accessing Array Elements​

#include <stdio.h>

int main() {
    int arr[5] = {10, 20, 30, 40, 50};

    printf("First element: %d\n", arr[0]);
    printf("Last element: %d\n", arr[4]);

    arr[2] = 35;
    printf("Modified third element: %d\n", arr[2]);

    printf("\nAll elements:\n");
    for (int i = 0; i < 5; i++) {
        printf("arr[%d] = %d\n", i, arr[i]);
    }

    return 0;
}

📝 Input and Output with Arrays​

#include <stdio.h>

int main() {
    int n, marks[50];

    printf("Enter number of students: ");
    scanf("%d", &n);

    for (int i = 0; i < n; i++) {
        printf("Student %d: ", i + 1);
        scanf("%d", &marks[i]);
    }

    printf("\nMarks entered:\n");
    for (int i = 0; i < n; i++) {
        printf("Student %d: %d\n", i + 1, marks[i]);
    }

    return 0;
}

🔍 Searching in Arrays​

int linearSearch(int arr[], int n, int key) {
    for (int i = 0; i < n; i++) {
        if (arr[i] == key) return i;
    }
    return -1;
}

🌀 Sorting Arrays​

void bubbleSort(int arr[], int n) {
    for (int i = 0; i < n - 1; i++) {
        for (int j = 0; j < n - i - 1; j++) {
            if (arr[j] > arr[j + 1]) {
                int temp = arr[j];
                arr[j] = arr[j + 1];
                arr[j + 1] = temp;
            }
        }
    }
}

🧵 Strings (Character Arrays)​

char name[50];
char greeting[20] = "Hello";
char message[] = "Welcome to C!";

🔢 Two-Dimensional Arrays​

int arr2D[3][3] = {
    {1, 2, 3},
    {4, 5, 6},
    {7, 8, 9}
};

🏆 Common Problems to Try​

  • 🔄 Reverse an array
  • 🥈 Find the second largest element
  • 🚫 Remove duplicates

⚠️ Limitations & Best Practices​

  • Size is fixed at compile-time
  • No automatic bounds checking (be careful!)
  • Use constants for array sizes
  • Always initialize arrays to avoid garbage values
#define MAX_SIZE 100
int arr[MAX_SIZE] = {0};

🎓 Quick Quiz​

What is the index of the first element in a C array?

  • 1
  • 0 ✅
  • -1