5.1. Recursion.   

A procedure or function which calls itself either directly or indirectly (A calls B which calls A, etc.) 


      integer function factorial(integer n);

      begin

            if n=0 then factorial  1

            else factorial  factorial(n-1)*n;

      end;

We can see in recursive function factorial that we have an if ... then ... else construct. This is typical of a recursive algorithm.