Data Structure & Alogrithm Lab

1. What is an Array?

Array ek aisa data structure hai jisme same data type ke multiple elements ko ek hi naam ke under store kiya jata hai.

Example:

int a[5];

Iska matlab hai:

• a → array ka naam

• int → data type ( Int, String, Boolean etc )

• [5] → maximum 5 integer elements

Index → elements ko identify/access karne ke liye use hota hai.

C language mein index hamesha 0 se start hota hai.

Element	Index	Reference
1st	0	a[0]
2nd	1	a[1]
3rd	2	a[2]
4th	3	a[3]
5th	4	a[4]

In simple Last index = Array Length − 1

Arrays Can Store Different Data Types

Array sirf int ka hi nahi hota. Different data types ke arrays bana sakte hain.

Integer Array

int marks[5];

Character Array

char name[20];

Float Array

float price[10];

Structure Array

struct Student students[50];

Lets do the code

#include <stdio.h> /*for Standard Input Output.*/

int main()
{
    int a[2] = {10, 20, 30};

    printf("First element = %d\n", a[0]); /*printf() → to display output*/
    printf("Second element = %d\n", a[1]);
    printf("Third element = %d\n", a[2]);

    return 0;
}

scanf() → to take input

printf() → to display output

1. Array Declaration

int a[3] = {10, 20, 30};

This is the most important line for understanding arrays.

• int

int

It means the array will store integer values.

• a

a

This is the name of the array.

• [3]

[3]

This means the array can store 3 elements.

• {10, 20, 30}

These are the values stored inside the array.

So the array looks like this:

Index	Value
0	10
1	20
2	30

⚠️ Remember: Array indexing starts from 0.

⭐ Most Important Thing to Remember

If you write:

int a[3] = {10, 20, 30};

There are 3 elements, but the indexes are:

0, 1, 2

Not:

❌ 1, 2, 3

1. return 0;

return 0;

This tells the operating system:

The program finished successfully. ✅

0 generally indicates successful execution.

This is not the Link this shows that ur code how to visualize the code line by line if error comes its show also

https://programiz.pro/code-visualizer/c

Exam ke liye Important Points

1. Array is a collection of elements of the same data type.

2. Array elements ko index ke through access kiya jata hai.

3. C language mein array indexing 0 se start hoti hai.

4. Last index = length − 1.

5. int a[5] mein 5 elements store ho sakte hain.

6. int a[5] ke valid indexes 0, 1, 2, 3, 4 hain.

7. int b[5][6] ek two-dimensional array hai.

8. b[5][6] mein total 30 elements ho sakte hain.

9. 2D array ka first element b[0][0] hota hai.

10. 2D array ka last element b[4][5] hota hai.

11. Arrays int, char, float, structure, etc. ke ho sakte hain.

🧠Easy Trick

C Array = Same Type + Same Name + Multiple Values + Index starts from 0

int a[5]

       0    1    2    3    4
      ↓    ↓    ↓    ↓    ↓
     [10] [20] [30] [40] [50]

a[0] = first element

a[4] = fifth/last element