Passing array to function in C programming with example

Just like variables, array can also be passed to a function as an argument . In this guide, we will learn how to pass the array to a function using call by value and call by reference methods.

To understand this guide, you should have the knowledge of following C Programming topics:

1. C – Array
2. Function call by value in C
3. Function call by reference in C

Passing array to function using call by value method

As we already know in this type of function call, the actual parameter is copied to the formal parameters.

#include <stdio.h>
void disp( char ch)
{
   printf("%c ", ch);
}
int main()
{
   char arr[] = {'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j'};
   for (int x=0; x<10; x++)
   {
       /* I’m passing each element one by one using subscript*/
       disp (arr[x]);
   }

   return 0;
}

Output:

a b c d e f g h i j

Passing array to function using call by reference

When we pass the address of an array while calling a function then this is called function call by reference. When we pass an address as an argument, the function declaration should have a pointer as a parameter to receive the passed address.

#include <stdio.h>
void disp( int *num)
{
    printf("%d ", *num);
}

int main()
{
     int arr[] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 0};
     for (int i=0; i<10; i++)
     {
         /* Passing addresses of array elements*/
         disp (&arr[i]);
     }

     return 0;
}

Output:

1 2 3 4 5 6 7 8 9 0

How to pass an entire array to a function as an argument?

In the above example, we have passed the address of each array element one by one using a for loop in C. However you can also pass an entire array to a function like this:

Note: The array name itself is the address of first element of that array. For example if array name is arr then you can say that arr is equivalent to the &arr[0].

#include <stdio.h>
void myfuncn( int *var1, int var2)
{
 /* The pointer var1 is pointing to the first element of
  * the array and the var2 is the size of the array. In the
  * loop we are incrementing pointer so that it points to
  * the next element of the array on each increment.
  *
  */
    for(int x=0; x<var2; x++)
    {
        printf("Value of var_arr[%d] is: %d \n", x, *var1);
        /*increment pointer for next element fetch*/
        var1++;
    }
}

int main()
{
     int var_arr[] = {11, 22, 33, 44, 55, 66, 77};
     myfuncn(var_arr, 7);
     return 0;
}

Output:

Value of var_arr[0] is: 11 
Value of var_arr[1] is: 22 
Value of var_arr[2] is: 33 
Value of var_arr[3] is: 44 
Value of var_arr[4] is: 55 
Value of var_arr[5] is: 66 
Value of var_arr[6] is: 77