Pass arrays to a function in C

In C programming, you can pass an entire array to functions. Before we learn that, let’s see how you can pass individual elements of an array to functions.

Passing individual array elements

Passing array elements to a function is similar to passing variables to a function.

Example 1: Passing an array

#include <stdio.h>
void display(int age1, int age2)
{
    printf("%d\n", age1);
    printf("%d\n", age2);
}

int main()
{
    int ageArray[] = {2, 8, 4, 12};

    // Passing second and third elements to display()
    display(ageArray[1], ageArray[2]); 
    return 0;
}

Output

8
4

Example 2: Passing arrays to functions

// Program to calculate the sum of array elements by passing to a function 

#include <stdio.h>
float calculateSum(float age[]);

int main() {
    float result, age[] = {23.4, 55, 22.6, 3, 40.5, 18};

    // age array is passed to calculateSum()
    result = calculateSum(age); 
    printf("Result = %.2f", result);
    return 0;
}

float calculateSum(float age[]) {

  float sum = 0.0;

  for (int i = 0; i < 6; ++i) {
		sum += age[i];
  }

  return sum;
}

Output

Result = 162.50

To pass an entire array to a function, only the name of the array is passed as an argument.

result =  calculateSum(age);

However, notice the use of [] in the function definition.

float calculateSum(float age[]) {
... ..
}

This informs the compiler that you are passing a one-dimensional array to the function.

Passing Multidimensional Arrays to a Function

To pass multidimensional arrays to a function, only the name of the array is passed to the function(similar to one-dimensional arrays).

Example 3: Passing two-dimensional arrays

#include <stdio.h>
void displayNumbers(int num[2][2]);
int main()
{
    int num[2][2];
    printf("Enter 4 numbers:\n");
    for (int i = 0; i < 2; ++i)
        for (int j = 0; j < 2; ++j)
            scanf("%d", &num[i][j]);

    // passing multi-dimensional array to a function
    displayNumbers(num);
    return 0;
}

void displayNumbers(int num[2][2])
{
    printf("Displaying:\n");
    for (int i = 0; i < 2; ++i) {
        for (int j = 0; j < 2; ++j) {
           printf("%d\n", num[i][j]);
        }
    }
}

Output

Enter 4 numbers:
2
3
4
5
Displaying:
2
3
4
5

Note: In C programming, you can pass arrays to functions, however, you cannot return arrays from functions.