A Recursive function is a function that calls itself. And this process is called recursion. Pass by Value Pass by Reference Functions prototype compiler return type declared using void calling function

Let us see another example. The following example uses a function called square which writes the square of the numbers between 1 and 10.

#include <stdio.h>

int square(int x); /* Function prototype */

int main()
{
int counter;

for (counter=1; counter<=10; counter++)

printf("Square of %d is %d\n", counter, square(counter));
return 0;
}

/* Define the function 'square' */
int square(int x)
{
return x * x;
}

The output of this program will be displayed as follows:

The function prototype square declares a function that takes an integer parameter and returns an integer. When the compiler reaches the function call to square in the main program, it is able to check the function call against the function's definition.

When the program reaches the line that calls the function square, the program jumps to the function and executes that function before resuming its path through the main program. Programs that do not have a return type should be declared using void. Thus Parameters to the function may be Pass By Value or Pass By Reference.

A Recursive function is a function that calls itself. And this process is called recursion.

Pass By Value Functions

The square function's parameters in the previous example are passed by value. This means that only a copy of the variable has been passed to the function. Any changes to the value will not be reflected back to the calling function.

The following example uses pass-by-value and changes the value of the passed parameter, which has no effect on the calling function. The function count_down has been declared as void as there is no return type.

#include <stdio.h>
void count_down(int x);

int main()
{
int counter;

for (counter=1; counter<=10; counter++)
count_down(counter);
return 0;
}
void count_down(int x)
{
int counter;
for (counter = x; counter > 0; counter--)
{
printf("%d ", x);
x--;
}
putchar('\n');
}

The output of the program will be displayed as follows:

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