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Diffstat (limited to 'source/arduino/int.rst')
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1 files changed, 44 insertions, 61 deletions
diff --git a/source/arduino/int.rst b/source/arduino/int.rst index 2bb3bef..4bb876c 100644 --- a/source/arduino/int.rst +++ b/source/arduino/int.rst @@ -1,3 +1,5 @@ +.. highlight:: cpp + .. _arduino-int: int @@ -6,79 +8,60 @@ int Description ----------- -Integers are your primary datatype for number storage, and store a -2 byte value. This yields a range of -32,768 to 32,767 (minimum -value of -2^15 and a maximum value of (2^15) - 1). - - - -Int's store negative numbers with a technique called -`2's complement math. <http://en.wikipedia.org/wiki/2's_complement>`_ -The highest bit, sometimes refered to as the "sign" bit, flags the -number as a negative number. The rest of the bits are inverted and -1 is added. - - - -The Arduino takes care of dealing with negative numbers for you, so -that arithmetic operations work transparently in the expected -manner. There can be an unexpected complication in dealing with the -`bitshift right operator (>>) <http://arduino.cc/en/Reference/Bitshift>`_ -however. - - - -Example -------- - -:: +The ``int`` data type represents integers. Integers are your primary +data type for number storage, and store a 4 byte value. This yields a +range of -2,147,483,648 to 2,147,483,647 (minimum value of -2^31 and a +maximum value of (2^31) - 1; that's about negative 2 billion to +positive 2 billion). - int ledPin = 13; +An ``int`` stores a negative number with a technique called `two's +complement math +<http://en.wikipedia.org/wiki/Two%27s_complement#Explanation>`_\ . +The highest bit in an ``int``, sometimes refered to as the "sign" bit, +flags the number as a negative number. (See the linked article on +two's complement for more information). +The Maple takes care of dealing with negative numbers for you, so that +arithmetic operations work mostly as you'd expect. There can be an +:ref:`unexpected complication <arduino-bitshift-signbit-gotcha>` in +dealing with the :ref:`bitshift right operator (>>) +<arduino-bitshift>`, however. +Here is an example of declaring an ``int`` variable named ``ledPin``, +then giving it value 13:: -Syntax ------- + int ledPin = 13; -:: +The general syntax for declaring an ``int`` variable named ``var``, +then giving it value ``val``, looks like:: - int var = val; + int var = val; +.. _arduino-int-overflow: +Integer Overflow +---------------- +When ``int`` variables leave the range specified above, they "roll +over" in the other direction. It's like in the game *Pac-Man* -- when +Pac-Man goes past the right edge of the screen, he reappears on the +left, and when he goes past the left side of the screen, he reappears +on the right. Here are some examples:: -- var - your int variable name -- val - the value you assign to that variable - - - -Coding Tip ----------- - -When variables are made to exceed their maximum capacity they "roll -over" back to their minimum capacitiy, note that this happens in -both directions. - - - -:: - - int x - x = -32,768; - x = x - 1; // x now contains 32,767 - rolls over in neg. direction - - x = 32,767; - x = x + 1; // x now contains -32,768 - rolls over - + int x; + x = -2,147,483,648; + x--; // x now contains 2,147,483,647; rolled over "left to right" + x = 2,147,483,647; + x++; // x now contains -2,147,483,648; rolled over "right to left" See Also -------- - -- `byte <http://arduino.cc/en/Reference/Byte>`_ -- `unsigned int <http://arduino.cc/en/Reference/UnsignedInt>`_ -- `long <http://arduino.cc/en/Reference/Long>`_ -- `unsigned long <http://arduino.cc/en/Reference/UnsignedLong>`_ -- `Integer Constants <http://arduino.cc/en/Reference/IntegerConstants>`_ -- `Variable Declaration <http://arduino.cc/en/Reference/VariableDeclaration>`_ +- :ref:`unsigned int <arduino-unsignedint>` +- :ref:`char <arduino-char>` +- :ref:`unsigned char <arduino-unsignedchar>` +- :ref:`long <arduino-long>` +- :ref:`unsigned long <arduino-unsignedlong>` +- :ref:`Integer Constants <arduino-constants-integers>` +- :ref:`Variables <arduino-variables>` |