Recursion is the effective calling (and nesting) of the same function over and over again to derive the solution (i.e. the work is accomplished through each successive function call).

Recursion is often considered more elegant, yet less efficient (the underlying work the computer must perform tends to be greater).

Here is an example of recursion to compute the sum of the first 10 integers (0-9):

1

#include <stdio.h>
 
int increment(int, int);
 
int main()
{
        int i = 0;
        int sum = 0;
 
        sum = increment(i, 10);
 
        fprintf(stdout, "sum is: %d\n", sum);
 
        return(0);
}
 
int increment(int value, int max)
{
        if (value < (max - 1))
                value = value + increment(value+1, max);
 
        return(value);
}

This program, when executed, will output:

$ ./recursion
sum is: 45
$ 

On the other hand, iteration is more in line with how we're used to thinking (step by step, with each detail more tangible). The computer tends to work more in an iterative fashion, although solutions done iteratively may not appear as elegant as under other forms (recursion).

Here is an example of iteration to compute the sum of the first 10 integers (0-9):

1

#include <stdio.h>
 
int main()
{
        int i = 0;
        int sum = 0;
 
        for(i = 0; i < 10; i++)
                sum = sum + i;
 
        fprintf(stdout, "sum is: %d\n", sum);
 
        return(0);
}

This program, when executed, will output:

$ ./iteration
sum is: 45
$ 

Recursion, like the use of pointers, structs, inheritance, polymorphism, etc. really lends itself well to larger, more complicated problems.

In the current setting, the iterative example likely looks far simpler (less code overall). This in no way implies recursion is inferior, as outside of potential performance issues, it is an effective way to solve problems, and being able to think recursively can improve one's problem solving skills overall.