' From the Computer Mathematics Concepts text
' Mathematical Ideas, Ninth Edition, Section 4.2
' Russian Peasant Method for Integer Multiplication
' Written by Michael L. Jones, M. S., Spring 2002
' Suffolk County Community College, Brentwood, New York

' Plan of attack: Start with two integers, a and b.  If a is odd, add b to
' the product; if b is even, do nothing.  Take the integer part of a divided
' by 2, and double b.  Repeat until a=0, and the product will have been
' accumulated.

CLS

INPUT "What is the first factor"; x
INPUT "What is the second factor"; y

PRINT

a = x  ' Copies of original values so we can check our product later
b = y
p = 0  ' Initialize product

WHILE a > 0  ' We stop when a=0; a WHILE...WEND loop is efficient
 
  PRINT a, b,  ' Print current a and b and stay on that line
 
  IF a MOD 2 = 0 GOTO 1  ' Skip the next steps for even a

  PRINT "*";  ' a is odd, so we mark b with an asterisk to indicate addend
  p = p + b   ' Addend b is added to product

1  ' Line number for use with the GOTO above.  do the following for any a

  PRINT  ' End the printed line
 
  a = INT(a / 2)  ' Take the integer part of a/2
  b = b * 2       ' Double b

WEND  ' End of WHILE loop

' Print out results

PRINT
PRINT "The peasant method gives"; p
PRINT
PRINT "The actual product is"; x * y