1: # Program 1: simple loop printing numbers from 1 to 6.
  2: i = 1
  3: while i < 6:
  4:   print(i)
  5:   i += 1
  6: print()
  7: 
  8: print("Simple loop printing numbers from 1 to 6:")
  9: 
 10: 
 11: (*
 12:    Program 2:
 13:    computes the factorial of 6.
 14: *)
 15: 
 16: i = 1
 17: r = 1
 18: while i <= 6:      (* loop *)
 19:   r = i * r
 20:   i += 1
 21: print("Computing factorial of 6 =", r)
 22: print()
 23: 
 24: # Program 3: computing the 10-th fibonacci number.
 25: a = 0
 26: b = 1
 27: i = 0
 28: while i < 10:
 29:   t = b
 30:   b = a + b
 31:   a = t
 32:   i += 1
 33: print("Computing fibonacci of 10 =", a)
 34: print()
 35: 
 36: 
 37: # Program 4: checking whether a year is leap (i.e. there is February 29).
 38: 
 39: year = 1900
 40: 
 41: is_leap = (year % 4 == 0 and year % 100 != 0) or (year % 400 == 0)
 42: if is_leap:
 43:    print(year, "is_leap")
 44: else:
 45:    print(year, "is not leap")