sizeof

1. char 1
   int、float 4
   double 8

2. 指针 4

3. 数组 看大小

char a[2];cout<<sizeof(a);//2,1*2int b[2] ;cout<<sizeof(b);//8,4*2

4.结构体
与精度最高的对齐

//sizeof(test)=2 struct test{   char a;   char b;};//最高为sizeof(int)=4,sizeof(test)=8(6->8) struct test{   char a;   char b;   int c;};//最高位sizeof(double)=8,izeof(test)=16(6->16) struct test{   char a;   char b;   double c;};//sizeof(test)=8(6->8) struct test{   char a;   char b;   char* p;};