What is an Array? Passing Array as Function Argument with Program

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Definition of Array

An array is a collection of elements of the same data type stored in contiguous memory locations, accessed using a common name and an index (subscript).

Declaration Syntax:

data_type array_name[size];

Example: int marks[10]; — declares an array of 10 integers.

Key Properties:

• Array index starts from 0 and goes up to size - 1
• All elements occupy consecutive memory locations
• Elements are accessed using subscript notation: arr[0], arr[1], ...
• Size must be a constant expression (fixed at compile time)

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Passing Array as Function Argument

When an array is passed to a function, the base address (address of the first element) is passed, not a copy of the entire array. This is called pass by reference.

Three ways to declare a function receiving an array:

• As a pointer: void func(int *arr)
• As a sized array: void func(int arr[10])
• As an unsized array: void func(int arr[])

Important Points:

• Changes made to array elements inside the function affect the original array
• The size of the array is usually passed as a separate argument
• Only the base address is passed, making it memory efficient

Example of function call:

int marks[10];
sort(marks, 10);  // passing array name and size

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Program: Arrange 10 Integer Numbers in Ascending Order Using Function

#include <stdio.h>

// Function to sort array in ascending order (Bubble Sort)
void sortAscending(int arr[], int n) {
    int i, j, temp;
    for (i = 0; i < n - 1; i++) {
        for (j = 0; j < n - 1 - i; j++) {
            if (arr[j] > arr[j + 1]) {
                // Swap the elements
                temp = arr[j];
                arr[j] = arr[j + 1];
                arr[j + 1] = temp;
            }
        }
    }
}

int main() {
    int arr[10], i;

    // Input 10 integers
    printf("Enter 10 integer numbers:\n");
    for (i = 0; i < 10; i++) {
        scanf("%d", &arr[i]);
    }

    // Call function to sort
    sortAscending(arr, 10);

    // Display sorted array
    printf("Array in ascending order:\n");
    for (i = 0; i < 10; i++) {
        printf("%d ", arr[i]);
    }

    return 0;
}

Sample Output:

Enter 10 integer numbers:
45 12 89 33 7 56 21 98 64 10
Array in ascending order:
7 10 12 21 33 45 56 64 89 98

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How the Program Works

• The sortAscending() function receives the array and its size as arguments
• It uses Bubble Sort algorithm — repeatedly compares adjacent elements and swaps them if they are in wrong order
• Since the array is passed by reference (base address), the sorted result is directly reflected in main()
• Time Complexity: $O(n^2)$ in worst case

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Conclusion: Arrays provide efficient storage for homogeneous data. When passed to functions, only the base address is transferred, allowing functions to directly modify the original array — making sorting operations simple and memory efficient.