BOOL与bool区别

1、先查看定义：

 

BOOL是微软定义的宏，实际上是int型占4个字节，该定义位于VC目录下WINDEF.H、AFX.H，可以找到如下代码：

// WINDEF.H
typedef unsigned long       DWORD;
typedef int                 BOOL;
typedef unsigned char       BYTE;
typedef unsigned short      WORD;
typedef float               FLOAT;

// AFX.H
#define FALSE   0
#define TRUE    1
#define NULL    0

 

bool是C/C++关键字，关于MSDN2005帮助文档中，解释如下：

 

This keyword is a built-in type. A variable of this type can have values true and false. Conditional expressions have the type bool and so have values of type bool. For example,

i!=0

now has true or false depending on the value of

i

.

The values true and false have the following relationship:

 

When a postfix or prefix ++ operator is applied to a variable of type bool, the variable is set to true. The postfix or prefix -- operator cannot be applied to a variable of this type.

 

The bool type participates in integral promotions. An r-value of type bool can be converted to an r-value of type int, with false becoming zero and true becoming one. As a distinct type, bool participates in overload resolution.

 

2、定义BOOL与bool原因（TRUE FALSE 与 true false）

 

在查阅很多资料后，请教了这方面朋友侦探，下面是他的解释如下：

Koma 12:15:48
C语言中已经有true和false还有null,微软为什么还定义TRUE, FALSE, NULL?
侦探 12:19:42
因为true,false, null内存空间占用1
而TRUE, FALSE, NULL内存空间占用4
侦探 12:20:45
根据intel CPU的内存分页机制,4字节可以防止内存松散,防止产生更多的内存碎片,有利于数据的传输