Parallax BASIC Stamp 2e, Руководство по программированию

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BASIC Stamp Architecture – ABS, COS, DCD, ~, -
Page 64
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BASIC Stamp Programming Manual 2.0b
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www.parallaxinc.com
The Absolute Value operator (ABS) converts a signed (two’s complement)
16-bit number to its absolute value. The absolute value of a number is a
positive number representing the difference between that number and 0.
For example, the absolute value of -99 is 99. The absolute value of 99 is
also 99. ABS works on two’s complement negative numbers. Examples of
ABS at work:
Result VAR WORD
Result = -99 ' Put -99 (2's complement format) into Result.
DEBUG SDEC ? Result ' Display it on the screen as a signed #.
DEBUG SDEC ? ABS Result ' Display it on the screen as a signed #.
The Cosine operator (COS) returns the two’s complement, 16-bit cosine of
an angle specified as an 8-bit (0 to 255) angle. See the explanation of the
SIN operator, below. COS is the same in all respects, except that the cosine
function returns the x distance instead of the y distance. To demonstrate
the COS operator, use the example program from SIN, below, but
substitute COS for SIN.
The Decoder operator (DCD) is a 2
n
-power decoder of a four-bit value.
DCD accepts a value from 0 to 15, and returns a 16-bit number with the
bit, described by value, set to 1. For example:
Result VAR WORD
Result = DCD 12 ' Set bit 12.
DEBUG BIN ? Result ' Display result (%0001000000000000)
The Inverse operator (~) complements (inverts) the bits of a number. Each
bit that contains a 1 is changed to 0 and each bit containing 0 is changed to
1. This process is also known as a “bitwise NOT” and one's compliment.
For example:
Result VAR BYTE
Result = %11110001 ' Store bits in byte Result.
DEBUG BIN ? Result ' Display in binary (%11110001).
Result = ~ Result ' Complement Result.
DEBUG BIN ? Result ' Display in binary (%00001110).
The Negative operator (-) negates a 16-bit number (converts to its two’s
complement).
SYMBOL Result = W1
Result = -99 ' Put -99 (2's complement format) into Result.
Result = 100 ' Add 100 to it.
DEBUG Result ' Display Result (1)
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