typedef和define的主要區別

typedef char* string_t;#define string_d char*//#define String_d char * 只是做了個簡單的替換? typedef char *String_t 定義了一個新的類型//主要區別在於這種使用方式String_t a,b;String_d c,d; a,b ，c都是char*類型，而d為char類型// 翻譯過來（char*）a,b；char* a，b；//#ifdef String_d 還有#ifdef String_t, 那麼前者是真, 後者是假;也就是說ifdef只是檢查宏的//http://c-faq.com/decl/typedefvsdefine.html//#defines do have the advantage that #ifdef works on them (see also question 10.15). //On the other hand, typedefs have the advantage that they obey scope rules (that is, they can be declared local to a function or block). char a[]="hello";char b[]="world";string_t s1,s2;s1=a;s2=b;string_d s3,s4;s3=a;s4=b;//會報錯