erlang 各种数据类型占用的内存大小

用erlang的话讲，深入了解erlang不同数据类型所占的内存空间大小，是erlang高效编程的一个良好开始。
一个程序要运行，就要先描述其算法。描述一个算法应先说明算法中要用的数据，数据以变量或常量的形式来描述。每个变量或常量都有数据类型。
很多人都以为要把算法写得多精湛，才算高效编程，其实不然，细微处见功夫。
以下内容展示了erlang各种数据类型占用的内存大小。

Data type	Memory size
Small integer	1 word On 32-bit architectures: -134217729 < i < 134217728 (28 bits) On 64-bit architectures: -576460752303423489 < i < 576460752303423488 (60 bits)
Big integer	3..N words
Atom	1 word. Note: an atom refers into an atom table which also consumes memory. The atom text is stored once for each unique atom in this table. The atom table is not garbage-collected.
Float	On 32-bit architectures: 4 words  On 64-bit architectures: 3 words
Binary	3..6 + data (can be shared)
List	1 word + 1 word per element + the size of each element
String (is the same as a list of integers)	1 word + 2 words per character
Tuple	2 words + the size of each element
Pid	1 word for a process identifier from the current local node, and 5 words for a process identifier from another node. Note: a process identifier refers into a process table and a node table which also consumes memory.
Port	1 word for a port identifier from the current local node, and 5 words for a port identifier from another node. Note: a port identifier refers into a port table and a node table which also consumes memory.
Reference	On 32-bit architectures: 5 words for a reference from the current local node, and 7 words for a reference from another node.  On 64-bit architectures: 4 words for a reference from the current local node, and 6 words for a reference from another node. Note: a reference refers into a node table which also consumes memory.
Fun	9..13 words + size of environment. Note: a fun refers into a fun table which also consumes memory.
Ets table	Initially 768 words + the size of each element (6 words + size of Erlang data). The table will grow when necessary.
Erlang process	327 words when spawned including a heap of 233 words.

那么，一个word占多大的空间？
1> erlang:system_info(wordsize).
8通常情况下，32位系统占4字节，64位系统占8字节。

参考：http://blog.csdn.net/mycwq/article/details/16893209