https://wiki.c2.com/?ExampleForthCode

 \ Sample test session:
 CR 7 STARS	\ user types this line, output follows
 ******* ok
 CR 3 TRIANGLE  \ user types this line, output follows
 *
 **
 ***
  ok
 CR 6 TOWER	\ user types this line, output follows
 *
 **
 ***
 ****
 *****
 ******
 ******
 ******
 ******
 ******
 ******
  ok
 \ End of sample code and test session.