sizeof整數所占記憶體空間(32bitand64bit比較)－安於現狀

sizeof 整數所占記憶體空間 32bit or 64bit

用以下程式分別在32bit 和64bits編譯器底下執行

char str[] = "Hello" ;
char *p = str ;
printf("sizeof(str) = %d ", sizeof(str));
printf("sizeof(p) = %d ", sizeof(p));
printf("sizeof(short) = %d ", sizeof(short));
printf("sizeof(int) = %d ", sizeof(int));
printf("sizeof(long) = %d ", sizeof(long));
printf("sizeof(long long) = %d ", sizeof(long long));
printf("sizeof(size_t) = %d ", sizeof(size_t));
printf("sizeof(double) = %d ", sizeof(double));
printf("sizeof(long double) = %d ", sizeof(long double));

64bit

sizeof(str)     = 6                                                                                                                                                  

sizeof(p)     = 8                                                                                                                                                    

sizeof(short)     = 2                                                                                                                                                

sizeof(int)       = 4                                                                                                                                                

sizeof(long)      = 8                                                                                                                                                

sizeof(long long) = 8                                                                                                                                                

sizeof(size_t)    = 8                                                                                                                                                

sizeof(double)     = 8                                                                                                                                               

sizeof(long double)    = 16    

32bit

sizeof(str) = 6 //char字串
sizeof(p) = 4 //指標
sizeof(short) = 2
sizeof(int) = 4 //怕因環境影響程式,絕大多數int 64,32bit的編譯器是一樣的大小
sizeof(long) = 4
sizeof(long long) = 8

sizeof(size_t) = 4
sizeof(double) = 8
sizeof(long double) = 12 //看作long+double = 4 + 8 =12

補充

int a[10] => sizeof為40 (4*10)

64bit,32bit都是

char str[100] ; => sizeof為 1

64bit,32bit都是

指標的sizeof都是 4bytes(32) or 8bytes(64)

參考資料

http://blog.urdada.net/2008/04/18/85/

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