堆和栈的区别(3)

2.6 存取效率的比较

char s1[] = "aaaaaaaaaaaaaaa";

char *s2 = "bbbbbbbbbbbbbbbbb";

aaaaaaaaaaa是在运行时刻赋值的；

而bbbbbbbbbbb是在编译时就确定的；

但是，在以后的存取中，在栈上的数组比指针所指向的字符串(例如堆)快。

比如：

#include
void main()
{
char a = 1;
char c[] = "1234567890";
char *p ="1234567890";
a = c[1];
a = p[1];
return;
}

对应的汇编代码

10: a = c[1];
00401067 8A 4D F1 mov cl,byte ptr [ebp-0Fh]
0040106A 88 4D FC mov byte ptr [ebp-4],cl
11: a = p[1];
0040106D 8B 55 EC mov edx,dword ptr [ebp-14h]
00401070 8A 42 01 mov al,byte ptr [edx+1]
00401073 88 45 FC mov byte ptr [ebp-4],al

第一种在读取时直接就把字符串中的元素读到寄存器cl中，而第二种则要先把指针值读到edx中，在根据edx读取字符，显然慢了。

2.7小结：

堆和栈的区别可以用如下的比喻来看出：

使用栈就象我们去饭馆里吃饭，只管点菜（发出申请）、付钱、和吃（使用），吃饱了就走，不必理会切菜、洗菜等准备工作和洗碗、刷锅等扫尾工作，他的好处是快捷，但是自由度小。

使用堆就象是自己动手做喜欢吃的菜肴，比较麻烦，但是比较符合自己的口味，而且自由度大。

堆和栈的区别主要分：

操作系统方面的堆和栈，如上面说的那些，不多说了。

还有就是数据结构方面的堆和栈，这些都是不同的概念。这里的堆实际上指的就是（满足堆性质的）优先队列的一种数据结构，第1个元素有最高的优先权；栈实际上就是满足先进后出的性质的数学或数据结构。

虽然堆栈，堆栈的说法是连起来叫，但是他们还是有很大区别的，连着叫只是由于历史的原因。

http://t.163.com/event/info/eventId/-4054014659260679579http://t.163.com/event/info/eventId/8716079504765824448http://t.163.com/event/info/eventId/8470963592102662643http://t.163.com/event/info/eventId/-2287143357252463104http://t.163.com/event/info/eventId/7327815198175597698http://t.163.com/event/info/eventId/5332798139198162018http://t.163.com/event/info/eventId/5212677783326518562http://t.163.com/event/info/eventId/-8414497406437818667http://t.163.com/event/info/eventId/466022097989870039http://t.163.com/event/info/eventId/-6671326893047528761http://t.163.com/event/info/eventId/5988502945366661164http://t.163.com/event/info/eventId/4759028504871970132http://t.163.com/event/info/eventId/7466179874822061918http://t.163.com/event/info/eventId/424602007495631460http://t.163.com/event/info/eventId/-1112903610957972001http://t.163.com/event/info/eventId/7656755762593269591http://t.163.com/event/info/eventId/-2089755221267149346http://t.163.com/event/info/eventId/-1466584469436639088http://t.163.com/event/info/eventId/-8923116757238050825http://t.163.com/event/info/eventId/-7455891012501089996http://t.163.com/event/info/eventId/3228650449365324092http://t.163.com/event/info/eventId/-8247692186160835118http://t.163.com/event/info/eventId/-7708466573145045998http://t.163.com/event/info/eventId/-6214855000495271992http://t.163.com/event/info/eventId/-1220489420125055773http://t.163.com/event/info/eventId/2997477298393766995http://t.163.com/event/info/eventId/2575174696099955719http://t.163.com/event/info/eventId/932242803760647086http://t.163.com/event/info/eventId/-1117131236474314556http://t.163.com/event/info/eventId/1169367759718451648http://t.163.com/event/info/eventId/3961200691175027546http://t.163.com/event/info/eventId/2024575377368071409http://t.163.com/event/info/eventId/7588036623986839318http://t.163.com/event/info/eventId/-217453328493090174http://t.163.com/event/info/eventId/1464596085510983051http://t.163.com/event/info/eventId/5794422413780167044http://t.163.com/event/info/eventId/-8453571181253032683http://t.163.com/event/info/eventId/330019483365333110http://t.163.com/event/info/eventId/-8698190567575266298http://t.163.com/event/info/eventId/-4145609458314693271http://t.163.com/event/info/eventId/161059662820477991http://t.163.com/event/info/eventId/-1668393782447264190http://t.163.com/event/info/eventId/6971152366072062016http://t.163.com/event/info/eventId/-5610907083493214779http://t.163.com/event/info/eventId/-8725886645951000743http://t.163.com/event/info/eventId/-1717648789636884507http://t.163.com/event/info/eventId/3075538682082399840http://t.163.com/event/info/eventId/206007153356922134http://t.163.com/event/info/eventId/-8062047790743101634http://t.163.com/event/info/eventId/8670838222660101995http://t.163.com/event/info/eventId/-8300637193668184862http://xiaozhao.renren.com/detail/experience/1377093http://xiaozhao.renren.com/detail/experience/1377099http://xiaozhao.renren.com/detail/experience/1377107http://xiaozhao.renren.com/detail/experience/1377111http://xiaozhao.renren.com/detail/experience/1377127http://xiaozhao.renren.com/detail/experience/1377133http://xiaozhao.renren.com/detail/experience/1377141http://xiaozhao.renren.com/detail/experience/1377157http://xiaozhao.renren.com/detail/experience/1377163http://xiaozhao.renren.com/detail/experience/1377183http://xiaozhao.renren.com/detail/experience/1377189http://xiaozhao.renren.com/detail/experience/1377193http://xiaozhao.renren.com/detail/experience/1377197http://xiaozhao.renren.com/detail/experience/1377209http://xiaozhao.renren.com/detail/experience/1377211http://xiaozhao.renren.com/detail/experience/1377215http://xiaozhao.renren.com/detail/experience/1377223http://xiaozhao.renren.com/detail/experience/1377243http://xiaozhao.renren.com/detail/experience/1377245http://xiaozhao.renren.com/detail/experience/1377257http://xiaozhao.renren.com/detail/experience/1377263http://xiaozhao.renren.com/detail/experience/1377299http://xiaozhao.renren.com/detail/experience/1377307http://xiaozhao.renren.com/detail/experience/1377313http://xiaozhao.renren.com/detail/experience/1377321http://xiaozhao.renren.com/detail/experience/1377339http://xiaozhao.renren.com/detail/experience/1377349http://xiaozhao.renren.com/detail/experience/1377357http://xiaozhao.renren.com/detail/experience/1377361http://xiaozhao.renren.com/detail/experience/1377385http://xiaozhao.renren.com/detail/experience/1377393http://xiaozhao.renren.com/detail/experience/1377407http://xiaozhao.renren.com/detail/experience/1377409http://www.zhihu.com/collection/24896107http://www.zhihu.com/collection/24896350http://www.zhihu.com/collection/24896458http://www.zhihu.com/collection/24896552http://www.zhihu.com/collection/24896659http://www.zhihu.com/collection/24896954http://www.zhihu.com/collection/24897199http://www.douguo.com/cookbook/444513.htmlhttp://www.douguo.com/cookbook/444527.htmlhttp://www.douguo.com/cookbook/444545.htmlhttp://www.douguo.com/cookbook/444562.htmlhttp://www.douguo.com/cookbook/444577.htmlhttp://www.douguo.com/cookbook/444616.htmlhttp://www.douguo.com/cookbook/444628.htmlhttp://www.douguo.com/cookbook/444643.htmlhttp://www.douguo.com/cookbook/444656.html