Parallax BASIC Stamp 2e - Multiply High (**); Multiply Middle (*;)

BASIC Stamp Architecture – **, */
Page 68 • BASIC Stamp Programming Manual 2.0b • www.parallaxinc.com
than 65535, the excess bits will be lost. Multiplication of signed variables
will be correct in both number and sign, provided that the result is in the
range -32767 to +32767.
SYMBOL Value1 = W0
SYMBOL Value2 = W1
Value1= 1000
Value2= 19
Value1= Value1 * Value2 ' Multiply Value1 by Value2.
DEBUG Value1 ' Show the result (19000).
-- or --
Value1 VAR WORD
Value2 VAR WORD
Value1= 1000
Value2= - 19
Value1= Value1 * Value2 ' Multiply Value1 by Value2.
DEBUG SDEC ? Value1 ' Show the result (-19000).
The Multiply High operator (**) multiplies variables and/or constants,
returning the high 16 bits of the result. When you multiply two 16-bit
values, the result can be as large as 32 bits. Since the largest variable
supported by PBASIC is 16 bits, the highest 16 bits of a 32-bit
multiplication result are normally lost. The ** (double-star) instruction
gives you these upper 16 bits. For example, suppose you multiply 65000
($FDE8) by itself. The result is 4,225,000,000 or $FBD46240. The * (star, or
normal multiplication) instruction would return the lower 16 bits, $6240.
The ** instruction returns $FBD4.
SYMBOL Value1 = W0
SYMBOL Value2 = W1
Value1= $FDE8
Value2= Value1 ** Value1 ' Multiply $FDE8 by itself
DEBUG $Value2 ' Return high 16 bits.
-- or --
Value1 VAR WORD
Value2 VAR WORD
Value1= $FDE8
Value2= Value1 ** Value1 ' Multiply $FDE8 by itself
DEBUG HEX ? Value2 ' Return high 16 bits.
The Multiply Middle operator (*/) multiplies variables and/or constants,
returning the middle 16 bits of the 32-bit result. This has the effect of
multiplying a value by a whole number and a fraction. The whole number
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MULTIPLY HIGH
: **
MULTIPLY MIDDLE: */
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