factorial using pipes

[ph2011]

write a program that calculates the factorial of an integer using pipes...
can me out with this problem..
thank you

[kfmfe04]

forget the pipes for the moment - how would you write a program which takes an integer from stdin and writes something useful for factorial to stdout?

keeping in mind:
f(n) = n!, where n! = n * (n-1) * ... * 1

so:
f(n) = n * f(n-1), n>1
f(1) = 1

[ph2011]

thank for that information..